I'm having an issue too... made a post in the general Black Ops section, but apparently I put it in the wrong spot because I'm an xBox player.  The Live website says there is a "subset" of users that will be unable to connect and are currently working on the issue... but I doubt it will be resolved any time soon.

WARzH311ion wrote:

 

Service alert
Service Details
     
     
Xbox LIVE:
     
Users may experience difficulties with the following services:

    A subset of users will be unable to connect to Xbox LIVE.

We are aware of the problem and are working to resolve the issue. We apologize for any inconvenience this may cause and thank you for your patience
Xbox LIVE Marketplace: Up and Running
Account: Up and Running
Matchmaking: Up and Running

just a little suggestion maybe change the defcon settings cause its not defcon 5

Ya i've had this problem for weeks now! I've called Activision and they told me i had to open more ports. So i went ahead contacted my internet service provider and got them all open. It worked for a bit, and now it's doing fudge all! It's like its picking and choosing when it works! and its funny how they tell you to go to their status page, and the server appears to be immaculate! yaaaaa right. I don't get it. I have friends across the street from me who can get into multiplayer anytime without any problems so why just me? everyones pointing the finger! xbox says its activision and activision says its xbox! Fix ur dam server! I'm sick of being on the phone with both these companies for hours and hours to get no where! this is a sad day