Periodic HTTP 500 Erorr on JBoss

We deploy the boe.war file to a Jboss application server for use on a custom app. After upgrading to BOBI 4.2 SP 8 P 3, periodically the user would see a HTTP 500 error when they click on a report in our application. To fix this we not stop and start te jboss server, but we also clear the temp files. This happens once or twice a week.
is this a JBoss error or BO? How do I resolve it so it doesn’t occur? Thanks
conrado