Hey Buddy, A friend of mine just resently suffered the very same problems and Steel hit it right on the head follow these procedures and good luck...
1. Make sure his cod/main and cod/uo directories are cleaned out; no mods, no files that don't belong there. I know you said his game is new, but if he already had cod then there might be junk in it. By the way, he does know that he needs both cod and coduo to play coduo, yes?
2. The 1.5 patch that included all previous patches is here
http://www.callofduty.com/patch/ 3. Then, here is a download location for the coduo 1.51 patch.
http://www.gamershell.com/download_7850.shtml4. He can always uninstall and reinstall the game, which often works to fix problems. However, the correct way to do this is to do an uninstall, either from the game's uninstaller or via add/remove programs. And then completely delete the Call of Duty folders. Lots of folks don't know that doing an uninstall leaves the folders on the hard drive, so that if you don't delete them, when you reinstall, you have exactly the same problems as before you started, lol. You must manually delete the Call of Duty folders.
Good luck to your bud.
BTW, if he's actually trying to install more than one copy of cod & coduo on his hard drive, that's a different story.