AndrewD. I have had the same problem with a Belkin N1 router. I bought it about 2 weeks ago and gave it back eventually. I am now still running on my old Belkin G Plus MIMO router. Having done a lot of searching (not a subject with a lot of straight answers) I have come to the conclusion that theres nobody who can give a specific answer. All comments seem personal views. I am currently running two xbox360's at the same time(two accounts). Unfortunately I can only get one with open NAT at any one time so I decided that a new router could be the solution. So theres good news and bad news. The good news is that you could easily run 1 xbox360 with open NAT and no game lag using the same as my old router. Now heres the bad news. If like me you are looking for the best you can get you will have to fork out around £180 quid for a Dlink DIR 855(as advertised on Overclockers). This router is the mother of them all but with a hefty price to go with it. I'm gonna wait to see if the price comes down but when it does I'll be first in the queue to get one. As a tip, you need to configure your DMZ if you have that option, as the ports, for the xbox to work best, need to be open, but dont open ports manually at the same time as they will conflict. It seems a lot of people are doing both and it only works if you use one or the other. Hope this helps.