First, I suspect that the game is installed on an NTFS partition. This can cause corruption during the install or patching process. It's possible that installing in Safe Mode might prevent that. That would be your primary problem, however....

I fear that the corruption in the game engine might have been placing bad information in your Savegames, in which case fixing the first problem wouldn't correct your current game. But maybe your Savegame is fine. Try either re-installing in Safe Mode or creating a FAT32 partition and let us know how it goes. Thanks!