Hi ctuai,
May I ask if the game crashes to the desktop when you try to do these things? If it does, then there is a possibility that it may be a problem with your graphics card's newer drivers or simply your graphics card rather than a horrible issue with your CD-Key - M:TW has a horrible intolerance for newer drivers and cards. Just incase this may be the nasty problem preventing you from playing this brilliant game, may I suggest that you attempt to follow the instructions in this thread should you have a Nivida card. Hopefully, it will resolve your problem so you can simply play this great game to it's full capacity! Hope this helps, my sincere appologies if I'm wrong, cheers!