What Country/State/Province do you live in? California, United States
Modem brand & model number: Speedstream 5100b
Router brand & model number: n/a
Network Connection Type: Wireless/Wired: Wired
If Wireless, what type of encryption are you using? n/a
Things you have tried: all listed on support page
1. power cycling
2. plugged directly into modem as always
3. Changed MTU to 1490 as recommended
4. Checked all connections
Is UPnP Enabled? Yes/no/Unknown: unknown Enabled where? I'm plugging directly into modem.
Is NAT Type Open? n/a
Any Error Codes you encounter: Insufficient MTU
What type of internet do you have? Cable/DSL/T1/3G? ADSL
Who is your ISP(Internet Service Provider)? ATT
When you run "Test Xbox LIVE connection" what is the exact message shown on screen?
Your network connection has insufficient MTU. MTU must be at least 1364. Change settings or plug directly into modem.
Endlessly turning the power off and on doesn't appear to be magically fixing this. The XBox 360 does not advertise itself as being only for network engineers. I'll keep this in mind for future purchases.