>>They share the VFP9 runtimes and the XiTech Cryptor library. But it seems to only happen when the communicating exe hits a comms snag. For example, yesterday my comms was very poor and the comms exe showed "Not Responding" in the title bar as Windows will do in such circunstances. The other exe then became unresponsive too. When the comms exe responded and continued again the other exe also responded as well. Could the cause be linked via the runtimes?
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>What else do they share?

I checked now and see that both EXEs also linked in wwipstuff.dll from WestWind but the output app does not actually use it for anything. I think I might have put it in for some function that never got built. I have removed it from the output EXE now.

Other than the VFP runtime DLLs and wwipstuff.dll and Cryptor there are no other DLLs.

Do you think that wwipstuff.dll could be the cause since after all it is doing the comms?