Microsoft Research has released CHESS, an automated tool for finding errors like data-races, deadlocks, and hangs in multithreaded applications by systematically exploring thread schedules (it has even discovered bug in PLINQ). Once error is located, CHESS provides a fully repeatable execution of the program leading to the error. Win32 version can be downloaded here (at this time license is only for academic use) and commercial version will hopefully be available soon.