I got the following error when I try to play the Call of Duty (multiplayer mode):
Unable to connect to activision matchmaking error 33.
Anybody have any information about this problem?
This error is generally related to the network being down, or the game servers being down. The only real solution to it is to wait and try again later.
The other issue that people have had with this error is a problem with their own router. You may need to turn off UPnP on your router.