I'll get the prerequisites out of the way first
What Country/State/Province do you live in? New Zealand (formerly Pittsburgh, Pennsylvania)
Modem brand & model number: Netcomm NB6plus4wn
Router brand & model number: Same as above (modem is router/router is modem)
Network Connection Type: Wireless/Wired (tried both)
If Wireless, what type of encryption are you using? (802.11g)
Things you have tried: See below
Is UPnP Enabled? Yes/no/Unknown (Yes)
Is NAT Type Open? (Yes)
Any Error Codes you encounter: See below
What type of internet do you have? Cable/DSL/T1/3G? (ADSL2)
Who is your ISP(Internet Service Provider)? (Watchdog)
When you run "Test Xbox LIVE connection" what is the exact message shown on screen? Insufficient MTU or Open Port 3074
Alright, so we've lived in New Zealand for over a year, had XBL for 7 months, and for the first 5 months everything worked fine, despite the occasional disconnect from XBL mid-game.
2 months ago the router went bad, and ever since we've replaced it with the Netcomm router nothing has been the same. We live in a church presbytery so the router is used by the whole office staff, and until recently we had no consistent internet connection to speak of. Finally, after 3 technicians and several phone-ins to the ISP and phone line provider, the internet problem *seems* to be solved. We haven't had a disconnect in 3 days (used to be at least 5 per day!).
We've had no XBL since the new router. Despite having a technician visit, and walking through router settings with another technician, we've not been able to eliminate the MTU settings error message. When we've changed the MTU, it gives us the "Open Port 3074" message. Ok, we've done that and opened the other ports suggested as well, but to no avail. I've plugged the console into the wired network, still hitting the MTU barrier.
I've been at this for over a month, tried every angle (I think), anyone have any ideas?? Thanks!