Many of you have this problem, I was one of you before, the way I fixed this problem is very easy.

1. Go to your router's menu. (you need to know your USER NAME and PASSWORD)

2. Go to FIREWALL setting ( Not the one in Windows) , and OPEN ALL YOUR PORTS, and click SAVE.

3. And now you should be able to play the game in MP.

And If many of you who is living in California want to shoot the REAl GUN, there was one GREAT class I have been to, just click the link to find out more, http://www.guninstruction.blogspot.com/