You may find that when you try to terminate a process on Windows 7, Windows Server 2008 R2, Windows Small Business Server 2011 SBS 2011 that the termination process stops responding. The main thread of the process becomes blocked and if you analyse the call stack of the process you will see that a thread is blocked in the ntdll!NtReleaseKeyedEvent() function. This occurs because of a race condition whereby the main thread that is trying to terminate the process also tries to reactivate another thread when the thread released an SRW lock.
This issue can be resolved by installing a hotfix containing an updated Ntdll.dll driver. You can find the hotfix download link in Microsoft KB 2582203 http://support.microsoft.com/kb/2582203