This is what I vaguely remember about CoD2. When you first install the game, you have to run multiplayer at least once before you patch it. All you have to do is open it up. Then you can quit it. Then you can run the patches.
I don't remember why this is, but I do remember having to do this myself. So you have to uninstall and start over.
Never had to do that....
nVidia graphics card? What driver version? There is a known problem with some recent drivers causing problems in CoD2, and UO.