I have a linksys wrt310v2 and i have upnp enabled, but I am still having trouble finding games at all times of the day. It is so bad that it won't even find a game and start a lobby with just me in it and where 7 other people have to join just to make it a game. This also was happening with modern warfare 2. if anyone could help it would be so so helpful.
the problem is when you plug your xbox in through the router rught? and its works fine with it straight in the modem right? are you sure your NAT is open when it is going through the router, because I have the same exact problem, that is solved when I run it straight through the modem instead of the router.