The same thing happened to me 2 and the problem was I had to copy save game files over from another pc in my network. Anyway, to rememdy this I very simply reinstalled it over the top of the old one (without a uninstall), put the official patches on and then it worked fine. So I presume you just need the savegame files there when youinstall it if this is your problem. If it wasn't caused by that may I suggest inserting the cd and going to setup.exe and reinstalling anyway as it might still work.
hope this solves your problem.
Spamfritter
