I am hit by this problem for almost one month and could not find a workable solution. This is my story...

My system consists of two application servers runng JBoss 5.0.1, a pair of oracle database servers running on RAC, and a couple of servers on a isolated network. Recently, I am conducting load test on this system with reasonably high amount of load to the application servers via web services. After running the tests for some times, one or both application servers seems to have lost connection with the oracle servers or test clients. I can restore the connectivity by restarting the network service on the "hung" application server and everything seems to work after that... until the next "hung". I think it is some by some network configuration. My reason to the system team for that is "how can application stop the network service?".

Other important information:
1) All the application servers have more than one Ethernet card for redundancy purposes, as well as connecting to servers in the isolated network.
2) When I am not able to putty to the "hung" server, I am able to connect it via another server via ssh using the internal ip address. It seems to me that only certain eth are disabled.
3) Due to this issue, I had disabled the syn flood cookie on all servers.
4) All application servers are load balanced by a pair of load balancers.