If you receive an XML error message upon launching the game, we would suggest deleting your Caches and Preferences folders as shown via the links below:
Deleting your Caches and Preferences Folders
Once you have completed these steps, launch the game.
If you're still having issues having done so, please Uninstall and Reinstall the game. Any save games will be left untouched during this process.
Edited by Neil Brock