One bug that we are aware of in JDeveloper 11g is that there is a memory leak if you do many repeat runs of an application.
However there is an easy way to eliminate most of those by changing the a setting in the specs for the integrated server.
Locate the file: setDomainEnv.cmd which should be at:
[JDev Install Dir]\jdeveloper\system\system126.96.36.199.31.51.88\DefaultDomain\bin
There find the line:
and change it to:
Now try and run your projects again.