COD MW2 I am unable to connect to a party. What is the problem and has anybody figured out how to correct it?

Unable to connect to host when receiving an invite or when trying to join a session. I'm really getting pissed because I first thought it was everybody. now I'm seeing clans online. Any suggestions?
Update: Thanks for answering. I have found a fix. Start the game. Then before you accept the invite sign out of PSN. Then sign in and accept the invite. You cannot open the invite before signing out.
Update 2: Thanks for answering. I have found a fix. Start the game. Then before you accept the invite sign out of PSN. Then sign in and accept the invite. You cannot open the invite before signing out.
2 answers 2