Black Ops - Ps3 Connection problems?

So when I had my NAT type at strict, the game was working fine, but my friends could not join me with invites or I could not join them, so I had my dad change the NAT type to moderate. My friends still cannot join me and I cannot join them, but also now every game I play I get disconnected. It says "Connection Interrupted" then it takes me back to the game lobby with players in it...apparently, then it says Game Lobby Closed. It does this EVERY game. How can I fix this problem, AND allow myself to play with friends?