Sounds like you may have the Blaster virus.
I thought about a virus, but what makes this problem unusual is that it started occurring sporadically (every few days) a couple of weeks ago. Now it occurs every time I turn on the computer.
Any suggestions for verifying the Blaster diagnosis? Do I need a very current version of Norton Anti-Virus to deal with this?
It sounds nothing like any of the blaster worms I've seen.