So I called the tech guy, and one of the things he told me was to unplug the modem for 30 seconds. I unplugged the power cord from the modem, plugged it back in, and nothing happened. After awhile, he got frustrated and told me to call Microsoft.

But afterwards, on a whim, I decided to unplug the power adapter from the other end--at the power surge protector--for some really weird reason that I can't figure out, that worked, but unplugging the power cord from the modem end didn't. Any ideas on why this is?
Well, today, the same thing happened...no Internet. So I unplugged the power adapter, but this time, even that didn't work. The only way I got it working again was to completely shut off *everything* and unplug the surge protector (which is what everything--computer, modem, monitor, etc is plugged into) from the wall. THEN it worked.
This is getting ridiculous...

Thanks to all who can help!