Permanent generation memory increases unlimited

[diego mec]

I have an application running on JBoss 4.0.5 on a HP-UX 11.23 system running java1.5.0.06.
The problem is that the permanent generation increases during normal execution of the application. Theoretically, it should remain more or less flat or stable once the application has started, but it does not do that. It starts around 50M and increases with no limit. If I set -XXPermSize=128 it can reach it very quickly (less than 1 minute) and lead to Full GC. If I set 256M or even 512M it also can reach it (if no System GC or full GC cuts it before.)
This affects to the heap sizing for I should first be able to control this permSize stuff.

Has anyone experience this behavior?
Is it a bug in the application? If this is the case, how can I detect it?

Thanks for your help