Playing MW2, my NAT is always set at Strict. I have fixed this a couple of times (first by enabling UPNP, then port forwarding, then setting up the 360 in a DMZ), however it has always reverted itself to Strict, even though these settings are supposed to permanently fix it.
So after trying all of these fixes I can only imagine that's it's a problem with the router. It's old, I got it 3 maybe 4 years ago and it wasn't the newest model back then.
So, assuming I'm right, I'm looking for recommendations on a new router. There are 3 other laptops connecting to it (wireless) as well as 4 other devices connected (wired). I'm using BT as my ISP, not sure if that makes a difference.