I just created my xboxlive account and found that I have a 'strict' NAT type. I found a solution online, typed in some numbers, applied some changes, and somehow now it says "Your NAT Type: Open". However, I am still unable to accept game invites from anyone nor send them successfully. I can play in any game and hear people Im playing with just fine, but can't play with my friends. I have no clue on what the problem is, any help is definitely appreciated.