I had the same problem. Oracle was started on the same port that by default JBoss uses (8080). Either change your JBoss port, or else change the Oracle port:
Run Start->Programs->Oracle OraHome92->Enterprise Manager Console and launch standalone.
Expand tree structure Network->Databases and select <DB SID>. Login as system user by right clicking and selecting 'Connect'. Remember to change the 'Connect as' list box to 'SYSDBA'
Further expand XML Databases and select Configuration.
Change the XML Database Parameter http-port from 8080 to 8081
If you want to see what application is currently using any port use netstat -oa if using Win XP, then lookup the PID from Task Manager. Better still, find fport from Google.