Xbox Live 'MTU' error

[Itchigon]

I got my replacement 360 back today and i set it up as my old one was. I plugged in my official wireless adapter and found my network. However when i test this network it connects to the router, connects to the internet but doesn't connect to Xbox Live.

The error says that my network doesn't have a sufficient MTU setting. Xbox live required a minimum MTU setting of 1364.

I don't see why i would be getting this error as my old 360 connected just fine to the exact same router (Actiontec GT701-WRU) and nothing has been changed on it. Anyone got any ideas?

I have already forwarded the necessary ports and tried uPnP and it still comes up with this error. Could it be the console that is causing the problem?

[MikeHaggar]

http://gamestm.co.uk/forum/viewtopic.php?f=11&t=13855

[Itchigon]

Tasty link there Mike thanks for the help!