Ronit,
Could it be that the external program is a shared program in a file server? This might cause file locking issues.
I'd suggest commenting the Run line of code and uncommenting the Sleep(5) command to simulate your program running the external program and waiting for it to finish. If the other PCs are still getting stuck then the calling program must be using some DB (or other) resource needed by the other PCs before the external program is executed.
Ricardo