Sorry to have to show my ignorance, here, but what's a "NIC"?

I'm connecting to the Internet through a dial-up, so I'm not sure that's an issue, but I understand what you're saying, now, about eliminating all the startup stuff and seeing if I still have a problem. I'll try that. My intuition on this, for what that's worth, is that this is some kind of timing issue -- Windows trying to do too many things at once. Just adding boot logging, whch I added to track down the problem, eliminated reboot issues for a while, though they have since returned.

I'll let you know if I get anywhere with disabling startup programs and drivers in msconfig.

Thanks,
David