JBoss 3.0 + Castor + Illegal Access Error

I quite often get this error. And after restarting the server (not always once, sometimes
after 2 or 3 times), everything start working perfectly..
Any answers ??
{CODE]
javax.transaction.TransactionRolledbackException: try to access method org
exolab.castor.mapping.loader.ClassDescriptorImpl.(Ljava/lang/Class

V from
class org.exolab.castor.mapping.loader.MappingLoader; nested exception is:
java.lang.IllegalAccessError: try to access method org.exolab.castor
mapping.loader.ClassDescriptorImpl.(Ljava/lang/Class

V from class org
exolab.castor.mapping.loader.MappingLoader
java.lang.IllegalAccessError: try to access method org.exolab.castor.mapping
loader.ClassDescriptorImpl.(Ljava/lang/Class

V from class org.exolab.castor
mapping.loader.MappingLoader
at org.exolab.castor.mapping.loader.MappingLoader.(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Native Method)
at org.exolab.castor.mapping.Mapping.getResolver(Unknown Source)
at org.exolab.castor.jdo.engine.DatabaseRegistry.loadDatabase(Unknown
Source)
at org.exolab.castor.jdo.JDO.getDatabase(Unknown Source)
at org.jboss.jdo.castor.CastorJDOImpl.getDatabase(CastorJDOImpl.java:276)
at com.softex.itesoverseer.server.ejb.dao.CastorMain
findCollection(CastorMain.java:136)
at com.softex.itesoverseer.server.ejb.dao.ServerDAO
findAllServers(ServerDAO.java:58)
at com.softex.itesoverseer.server.ejb.session.ClientManagerBean
getAllServers(ClientManagerBean.java:72)
at java.lang.reflect.Method.invoke(Native Method)
at org.jboss.ejb.StatelessSessionContainer$ContainerInterceptor
invoke(StatelessSessionContainer.java:664)
at org.jboss.resource.connectionmanager.CachedConnectionInterceptor
invoke(CachedConnectionInterceptor.java:186)
at org.jboss.ejb.plugins.StatelessSessionInstanceInterceptor
invoke(StatelessSessionInstanceInterceptor.java:77)
at org.jboss.ejb.plugins.AbstractTxInterceptor
invokeNext(AbstractTxInterceptor.java:96)
at org.jboss.ejb.plugins.TxInterceptorCMT
runWithTransactions(TxInterceptorCMT.java:167)
at org.jboss.ejb.plugins.TxInterceptorCMT.invoke(TxInterceptorCMT.java:61)
at org.jboss.ejb.plugins.SecurityInterceptor.invoke(SecurityInterceptor
java:129)
at org.jboss.ejb.plugins.LogInterceptor.invoke(LogInterceptor.java:166)
at org.jboss.ejb.StatelessSessionContainer.invoke(StatelessSessionContainer
java:313)
at org.jboss.ejb.Container.invoke(Container.java:705)
at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:491)
at org.jboss.invocation.local.LocalInvoker.invoke(LocalInvoker.java:98)
at org.jboss.invocation.InvokerInterceptor.invoke(InvokerInterceptor
java:102)
at org.jboss.proxy.TransactionInterceptor.invoke(TransactionInterceptor
java:73)
at org.jboss.proxy.SecurityInterceptor.invoke(SecurityInterceptor.java:76)
at org.jboss.proxy.ejb.StatelessSessionInterceptor
invoke(StatelessSessionInterceptor.java:111)
at org.jboss.proxy.ClientContainer.invoke(ClientContainer.java:76)
at $Proxy25.getAllServers(Unknown Source)
at com.softex.itesoverseer.server.servlet.action.ClientAction
execute(ClientAction.java:69)
at org.apache.struts.action.RequestProcessor
processActionPerform(RequestProcessor.java:437)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor
java:264)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1109)
at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:452)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:740)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.catalina.core.ApplicationFilterChain
internalDoFilter(ApplicationFilterChain.java:247)
at org.apache.catalina.core.ApplicationFilterChain
doFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.StandardWrapperValve
invoke(StandardWrapperValve.java:243)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline
java:566)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline
java:472)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
at org.apache.catalina.core.StandardContextValve
invoke(StandardContextValve.java:190)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline
java:566)
at org.apache.catalina.valves.CertificatesValve.invoke(CertificatesValve
java:246)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline
java:564)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline
java:472)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
at org.apache.catalina.core.StandardContext.invoke(StandardContext
java:2343)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve
java:180)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline
java:566)
at org.apache.catalina.valves.ErrorDispatcherValve
invoke(ErrorDispatcherValve.java:170)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline
java:564)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve
java:170)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline
java:564)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve
java:468)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline
java:564)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline
java:472)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve
java:174)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline
java:566)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline
java:472)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
at org.apache.catalina.connector.http.HttpProcessor.process(HttpProcessor
java:1012)
at org.apache.catalina.connector.http.HttpProcessor.run(HttpProcessor
java:1107)
at java.lang.Thread.run(Thread.java:484)
[/CODE]

Could this error be due to Classpath problem ?

Castor integrated with JBoss 3.0 gives this error repeatedly ! And disappears by mere restrating the server. Anyone facing this problem ?