mpiexec hang after program exit

Out product includes GUI and engine parts. Intel MPI  4.1 was used in engine code. GUI will can engine through mpiexec. Everything works fine on Windows 7 and Windows server 2008. When we run the product on Windows 8 and Windows server 2012, we met some problem. 

The code to start engine looks like CreateProcess( NULL, "mpiexec - n 2 engine", NULL, ........) . After engine exit, mpiexec still hang in memory and cannot exit. This will cause GUI hang. If we run the engine form command, mpiexec can exit after engine exit. 

I upgraded MPI from 4.1 to 5.0 and wrote a simple code to test on Windows 8. I ran the code with command.

    mpiexec -n 2 mysample.exe

This time, mpiexec cannot exit after mysample.exe exit.

Yongjun