Very odd connection error

[Simon Machin]

When I run a program that connects to a DB2 backend on it's own, it connects with no problems. When I use the class from another program (the calling class is running inside a jar file) it produces this error. All the properties are the same:
COM.ibm.db2.jdbc.DB2Exception: [IBM][JDBC Driver] CLI0600E Invalid connection handle or connection is closed. SQLSTATE=S1000
at COM.ibm.db2.jdbc.app.SQLExceptionGenerator.check_return_code(SQLExceptionGenerator.java:417)
at COM.ibm.db2.jdbc.app.DB2Connection.connect(DB2Connection.java:421)
at COM.ibm.db2.jdbc.app.DB2Connection.<init>(DB2Connection.java:324)
at COM.ibm.db2.jdbc.app.DB2Driver.connect(DB2Driver.java:352)
at java.sql.DriverManager.getConnection(DriverManager.java:512)
at java.sql.DriverManager.getConnection(DriverManager.java:172)
at signet.internet.catalogueutils.DeleteFreeProduct.<init>(DeleteFreeProduct.java:71)
at signet.internet.catalogueutils.DeleteFreeProduct.getInstance(DeleteFreeProduct.java:105)
at signet.util.SKUImport.SKUFileWatcher.processFileArrived(SKUFileWatcher.java:159)
at signet.util.FileWatcher.notifyFileArrived(FileWatcher.java:227)
It falls over at this line

try {
con = DriverManager.getConnection(jdbcURL, jdbcUserID, jdbcPassword);
} catch (SQLException sqle)
{
sqle.printStackTrace(); 
} 

I'm utterly stumped, any suggestions?
Cheers
James

[martin samm]

i presume you're running it on the same machine? i.e. can the machine giving the error 'see' the database? Also if it is a different database, is it restricted by IP? I'm not used to DB2, but certainly the above for Oracle would suggest the database has been brought down.