DOM-XML Parsing using an xsd-schema -> Error: Failed to read schema document

My application uses DOM-Parsing of XML documents and validates the xml documents via a xsd file. This works on my Development and test machines (Win XP/OSX 10.6) and on most pcs (homogenous XP business pcs) it was deployed to. Now one pc throws a SAXParseException(failed to read schema document). I've verified that the expected file is in the expected location. Please see below for an extract of the code in question and the stack trace. I'm not able to reproduce this behaviour on my machines. Any tips on debugging this or possible root causes appreciated.

private void importPlugin(File pluginConfigFile, String fullPath)
            throws DataPluginParseException {

try {
        
            String schemaLang = "http://www.w3.org/2001/XMLSchema";
            SchemaFactory schemaFact = SchemaFactory.newInstance(schemaLang);
            Schema schema = schemaFact.newSchema(new StreamSource(fullPath
                    + File.separator + "schema" + File.separator
                    + "DataPluginSchema.xsd"));

Validator validator = schema.newValidator();
            validator.validate(new StreamSource(pluginConfigFile));
...
...
}

/******************
the stack trace:
STDERR: org.xml.sax.SAXParseException: schema_reference.4: Failed to read schema document 'C:\Documents and Settings\xxx.yyy\My Documents\eigene Dateien\SiebelReport_SM\QBE\plugins\replugin\schema\DataPluginSchema.xsd', because 1) could not find the document; 2) the document could not be read; 3) the root element of the document is not <xsd:schema>.
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.error(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDHandler.reportSchemaErr(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDHandler.reportSchemaError(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDHandler.getSchemaDocument(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDHandler.parseSchema(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaLoader.loadSchema(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaLoader.loadGrammar(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaLoader.loadGrammar(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.jaxp.validation.XMLSchemaFactory.newSchema(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at javax.xml.validation.SchemaFactory.newSchema(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.server.impl.DomDataPluginParser.importPlugin(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.server.impl.DomDataPluginParser.buildDataPluginPropertyMap(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.server.impl.DataPluginPoolImpl.populateLists(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.server.impl.DataPluginPoolImpl.<init>(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.server.impl.DataServiceImpl.<init>(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.server.impl.DataServiceImpl.getInstance(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.impl.connector.server.DataServiceConnectorImpl.connectToDataService(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.impl.connector.server.DataServiceConnectorImpl.processClientEvent(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.impl.connector.server.DataServiceConnectorImpl.onEvent(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.impl.connector.server.DataServiceConnectorImpl.onEvent(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at org.bushe.swing.event.ThreadSafeEventService.publish(ThreadSafeEventService.java:971)
08.10.2010 14:47:18  
STDERR: 	at org.bushe.swing.event.ThreadSafeEventService.publish(ThreadSafeEventService.java:904)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.impl.client.QbeClientImpl.processUIExternalEvent(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.impl.client.QbeClientImpl.onEvent(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.impl.client.QbeClientImpl.onEvent(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at org.bushe.swing.event.ThreadSafeEventService.publish(ThreadSafeEventService.java:971)
08.10.2010 14:47:18  
STDERR: 	at org.bushe.swing.event.SwingEventService.publish(SwingEventService.java:78)
08.10.2010 14:47:18  
STDERR: 	at org.bushe.swing.event.ThreadSafeEventService.publish(ThreadSafeEventService.java:904)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.impl.client.userinterface.UserInterfaceImpl.run(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at java.awt.event.InvocationEvent.dispatch(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at java.awt.EventQueue.dispatchEvent(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at java.awt.EventDispatchThread.run(Unknown Source)
08.10.2010 14:47:18  
STDERR: qbebuilder.exceptions.server.DataPluginParseException: org.xml.sax.SAXParseException: schema_reference.4: Failed to read schema document 'C:\Documents and Settings\xxx.yyy\My Documents\eigene Dateien\SiebelReport_SM\QBE\plugins\replugin\schema\DataPluginSchema.xsd', because 1) could not find the document; 2) the document could not be read; 3) the root element of the document is not <xsd:schema>.
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.server.impl.DomDataPluginParser.importPlugin(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.server.impl.DomDataPluginParser.buildDataPluginPropertyMap(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.server.impl.DataPluginPoolImpl.populateLists(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.server.impl.DataPluginPoolImpl.<init>(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.server.impl.DataServiceImpl.<init>(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.server.impl.DataServiceImpl.getInstance(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.impl.connector.server.DataServiceConnectorImpl.connectToDataService(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.impl.connector.server.DataServiceConnectorImpl.processClientEvent(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.impl.connector.server.DataServiceConnectorImpl.onEvent(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.impl.connector.server.DataServiceConnectorImpl.onEvent(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at org.bushe.swing.event.ThreadSafeEventService.publish(ThreadSafeEventService.java:971)
08.10.2010 14:47:18  
STDERR: 	at org.bushe.swing.event.ThreadSafeEventService.publish(ThreadSafeEventService.java:904)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.impl.client.QbeClientImpl.processUIExternalEvent(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.impl.client.QbeClientImpl.onEvent(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.impl.client.QbeClientImpl.onEvent(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at org.bushe.swing.event.ThreadSafeEventService.publish(ThreadSafeEventService.java:971)
08.10.2010 14:47:18  
STDERR: 	at org.bushe.swing.event.SwingEventService.publish(SwingEventService.java:78)
08.10.2010 14:47:18  
STDERR: 	at org.bushe.swing.event.ThreadSafeEventService.publish(ThreadSafeEventService.java:904)
08.10.2010 14:47:18  
STDERR: 	at qbebuilder.impl.client.userinterface.UserInterfaceImpl.run(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at java.awt.event.InvocationEvent.dispatch(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at java.awt.EventQueue.dispatchEvent(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at java.awt.EventDispatchThread.run(Unknown Source)
08.10.2010 14:47:18  
STDERR: Caused by: org.xml.sax.SAXParseException: schema_reference.4: Failed to read schema document 'C:\Documents and Settings\xxx.yyy\My Documents\eigene Dateien\SiebelReport_SM\QBE\plugins\replugin\schema\DataPluginSchema.xsd', because 1) could not find the document; 2) the document could not be read; 3) the root element of the document is not <xsd:schema>.
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.error(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDHandler.reportSchemaErr(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDHandler.reportSchemaError(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDHandler.getSchemaDocument(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDHandler.parseSchema(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaLoader.loadSchema(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaLoader.loadGrammar(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaLoader.loadGrammar(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at com.sun.org.apache.xerces.internal.jaxp.validation.XMLSchemaFactory.newSchema(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	at javax.xml.validation.SchemaFactory.newSchema(Unknown Source)
08.10.2010 14:47:18  
STDERR: 	... 27 more
*******/

Have you checked whether the OS user that is executing the code on that machine has permission to read the file ?

No, I'll have to do this. But honestly, I can't imagine how this would be possible. All machines to which this application was deployed are business-machines in the same company with a homogenous-setup - this also applies to the user setup.

'C:\Documents and Settings\xxx.yyy\My Documents\eigene Dateien\SiebelReport_SM\QBE\plugins\replugin\schema\DataPluginSchema.xsd'

With Java applications, it's always a good idea to keep the files outside of folders which have a space in their path.

wow...
i never thought about it.
I thought if we want to parse the xml
JDOM has a smaller step to handle it.

just a small talk.