Are you using the GOG or Steam version?
I'm using the Steam version. Which was perhaps inadvisable, but I wanted the shiny of the achievements.
No, I would actually advise anyone who can use Steam to do so, the GOG distribution is a pain and easy to make mistakes with installation.
Have you tried uninstalling everything and starting from scratch? If you were playing the EA version and then tried to update to the release version without a clean uninstall and re-install, I think it increased your chances for some resource issues.
