I hope there are some expert computer techys around here who can help me with this problem.

When I use network bridging, following the guide at www.xboxlivetheguide.co.uk THOROUGHLY (I am bridging correctly so that is out of the question), I pass all the tests on my 360 except MTU. People have suggested using DRTCP.exe to set the MTU of my network adapter to the minimum Xbox live will allow and have also tried setting the MTU to 1492 (because apparently a high MTU can also cause this error), this gives me no success.

I don't know how this can be a router issue either because I can get Xbox Live to work fine on Windows ICS, (albeit through disabling and enabling ICS every time I reboot my PC). I thought Bridging was supposed to be MORE efficient.

I know you are all thinking, "Well if you can get it to work on ICS then what's the problem?". Well, the problem is I get a 'Strict' NAT which basically prevents me from joining 80% of the games on Live. Also, the connection quality is usually pretty terrible. I would much prefer it if I could get bridging to work.

Technical specs: Belkin Wireless Adapter 802.11g (latest drivers)
Nvidia Networking Controller (latest ethernet drivers)
Zyxel Prestige 650 Router (Internet Gateway)

Windows Vista 32bit
Intel Core 2 Quad @ 2.7ghz
Asus P5N32-E SLI Mobo
2GB Corsair XMS2 DDR2 800MHZ RAM
Geforce 8800GT

Microsoft clearly states that ICS is not suitable for Xbox live. Listen to them.