Blackbox testing of multithreaded programs

I test of multithreaded program. But i dont want to use unit testing method. I want to use blackbox method in my testing work. I know that for testing of multithreaded appl开发者_JS百科ication I have to use multicore processor, and give load for application and testing synchronization and locks between interfaces my program, but the bugs that I find can not repeat the developer. And it is most big problem for me. are there methods for blackbox testing multithreaded programs?

P.S. I test desktop application (use C# .Net)

There is CHESS (I don't believe it works with .NET 4.0 though):

CHESS is a tool for finding and reproducing Heisenbugs in concurrent programs. CHESS repeatedly runs a concurrent test ensuring that every run takes a different interleaving. If an interleaving results in an error, CHESS can reproduce the interleaving for improved debugging. CHESS is available for both managed and native programs.

CHESS: Find and Reproduce Heisenbugs in Concurrent Programs