Sorry but I can't.
Do you setup the Oracle by yourselve? Or do you have an admin for help?
A simple way to locate the problem is to use a SQL tool like SQirreL, it is easy to install and it is a JDBC client like JBoss.
Also check your connect data. Is the sqldeveloper connect the same?
It might possible that you add a wrong ojdbc...jar to jboss/lib (or even two )