I've only heard of this happening to people that have a NAT Type Strict, but apparently it can happen on Moderate too. You might want to try changing your NAT Type to Open by going into your router and forwarding the right ports to your PS3.
You must login or register to view this content. is a decent tutorial on how to do this. Opening your NAT should hopefully solve the problem, plus, having an Open NAT will benefit you even more, especially if you have a weaker connection since it gives it the best connection possible. :y:
If you don't feel like going through all that, you could simply just try change your Search Preferences on Black Ops to Locale or Locale Only. This has worked for others with this problem. Other than that, I'm afraid I don't know what to do, but one of those should (hopefully) work.