When you installed the software it might have written an older version of some DLL that is needed - sometimes Win7 warns you and sometimes it doesn't. There is a system file checker, which I believe is "sfc", but I don't know how to use it. Maybe a trip over to the Win7 forum to look up sfc would be helpful.
Unfortunately, uninstalling a program that overwrote a .dll file usually won't put the .dll back the way it was when you started.
I sounds like you re-installed the commserver? That would have been my next step. On some programs when you go to run install you will be presented with an option to repair the installation. If that shows up I would choose that.
Which version of Win7 do you have? If you have ultimate or the one step below it I know MS is giving away VirtualXP that you can install on there. I have that on mine, and it's pretty cool because you can actually run a virtual copy of XP from within Win7 and the XP has all its own programs, memory, etc - it's pretty slick. If nothing else maybe you could run your software under there? It's easier than dual boot because when you shutdown XP you are right back to your Win7 screen, and you can toggle back and forth.
You might also try right clicking on your commserver program icon and telling Windows to run it in XP compatibility mode - maybe that will work.
Just some additional thoughts - maybe one will help....