I think your app has been made with a paradox version for Windows 9x, so it runs well in Win 2k which has a good app compatibility mode that mimicks win9x and not in win nt which doesn't have it.
If you cannot upgrade your apps to a more recent version of Pdox, because you don't have the source, you're stuck with win 2k; the other way, you can easily recompile it, you should have no problem in recompiling apps made with Pdox 7> in Pdox 11.