When Bamboo runs for some time (lets say 10 builds) it hangs repdroducbily directly after a build. The sympton is, that no one can connect to
the webapp anymore, blocking for ever. After 8 minutes or so, the following appears in atlassian-bamboo.log:

2007-02-23 14:47:10,603 INFO [BAM:Default Queue:BuildExe] [SaveBuildTask] Indexing build results...
2007-02-23 14:55:45,547 INFO [SocketListener0-254] [SocketListener] LOW ON THREADS ((256-255+0)<2) on SocketListener0@0.0.0.0:8085
2007-02-23 14:56:00,566 WARN [Acceptor ServerSocket[addr=0.0.0.0/0.0.0.0,port=0,localport=8085]] [ThreadPool] No thread for Socket[addr=/127.0.0.1,port=56277,localport=8085]
2007-02-23 14:56:10,569 WARN [Acceptor ServerSocket[addr=0.0.0.0/0.0.0.0,port=0,localport=8085]] [ThreadPool] No thread for Socket[addr=/127.0.0.1,port=56278,localport=8085]
2007-02-23 14:56:20,573 WARN [Acceptor ServerSocket[addr=0.0.0.0/0.0.0.0,port=0,localport=8085]] [ThreadPool] No thread for Socket[addr=/127.0.0.1,port=56279,localport=8085]
....

and so on.

A restart is the only workaround for the moment