Phuuu
After checking almost every possible solution I finally found out, that the time out is not a sever problem, but an application problem.
It's the Flex part which generates a time out error if the server doesn't respond during 2 minutes. No i just have to find out, how I add a possibility to give all 2 minutes a feedback, so the application knows, that the server is still working.
But that I have to find out in an other forum.
I want to thank you all for your help!!! It really helped to understand the JBOSS Server a lot better.