Looking at the Black Ops forum this game much like many new releases seems to be plagued with problems.
Reading one of the forums it seems you can’t change your loadout or class after you join a game without having to back all the way out. From what I also read you have to also wait for the server to update with the change before you can log in. WTF? Also they are saying that you have to go with what maps are on that dedicated server, can’t change? But apparently on the console versions you have more options. Interesting!