Sorry to dig, but this should help the previous poster
Something has gone wrong with your update to 1.85.3, or you have a mod in there (not necessarily activated) that has interfered with your .pat files which dictate the last .X number
The only thing i can suggest you do to get 1.85.3 on your system is to wipe the game, clear the installation directory, and reinstall, patching to 1.85.3 as soon as install is complete and before running the game.
If you are on steam, simply delete local content, then reinstall, it will patch automatically.
You can keep your player profile data in your My Documents/Documents directory in both cases, but your saves wont carry over patch to patch