I had the exact same problems for my Xbox 360, I just opend up DMZ for my 360 and that works brilliant, saves you putting in every port, there aren't any security issues doing this for your games cons ...
IM SO HAPPY YOU GUYS HAVE THE SAME PROBLEM.
Not in a bad way lol but ive been struggling with this for months!
Im with Orange and have the livebox etc and i often play my xbox and pc.
I play a lot ...