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http://www.callofduty.com/blackops/faq/ioszombies
Had the same problem. Try here (port forwarding section): http://www.callofduty.com/blackops/faq/ioszombies Have fun!
@JuiceTha9FiftyFive wow man..that WORKED FOR me! I can now play non-stop online!!!!!! Amazing tip thanks a lot!