Since the launch of cod black ops there have been so many issues with playing online! Most people are blaming it on firewall or router issues even networking ports need opening and forwarding if this is the case i will find the solution and post it up here. If you have any other issues with the game feel free to post it up in here.
Some of the most common. Host migration - Connection interrupted. Other issues inviting friends to your lobby or parties is almost impossible behind a router if the NAT is set to strict.