You could possible look at the readme.txt of the game. It should show the version number. Note: If a patch only partially installed, it could have changed the version number, without changing something else. I've had this problem. I can't update my game, every patch only partially works thus breaking the half game. I use GoBack to undo the patch, but I think you will have to uninstall, then reinstall the game.
1) Try to reinstall patch 1.2, then play online.
2) Try to install patch 1.3, then play online.
3) If those don't work, uninstall then reinstall the game and try playing online with out any patches. If you can play online now, you know where the problem was (patch 1.2)