My mate has a 3G phone, which he's plugged into a vista laptop. He can use internet, MSN and webcam fine, speeds should be good for gaming. He's then got a network cable plugged from the laptop into the Xbox 360. We've tried setting up ICS (Internet Connection Sharing) on the connection for the internet and this seemed to work, he setup a Live account and all looked good, untill we tried to join a party or play a game, he then got the infamous "NAT set to Strict" error message and can't play, etc.

Apparently you can't alter the NAT to Open if you are using ICS, is this true?

A suggestion on the net was to use Bridging instead, but when we bridge the two connections (Internet and connection to Xbox) his internet connection goes down. No amount of tweaking (and we spent over 10 hours yesterday trying) seems to fix it.

Most people will just say, use a router, but that is not an option as he needs to use his phone.

Please, please, has anyone got any suggestions?