SUMMARY: For two nights in a row, my Win XP SP3 computer has rebooted between 10:30 and 12:00 midnight ... and, on power up, has given weird (to me) MAC DHCP error messages (which I should have copied down, and didn't).
DETAILS: Because of a graphics card problem, I log off my computer, rather than shut it down. I work in a home office environment, and am accustomed to logging off at 10:30 p.m. or so and then seeing the log on prompt again in the morning when I return to work.
The night before last, at almost midnight, I happened to notice that the mouse light wasn't lit. I turned on the monitor and, surprise surprise, the computer had rebooted. I was looking at the computer's power-on password prompt, rather than the Win XP log on prompt ... even though the computer gets power through an APC UPS.
"That's odd," I thought, and entered the power-on password ... and then scratched my head as weird (to me) messages related to "MAC address" and "DHCP client" filled the screen.
I soft rebooted; same thing. My computer wasn't loading Win XP. It was delivering these messages related to MAC address and DHCP client.
I turned the computer physically off, then restarted ... and this time the computer loaded Win XP normally.
"What a weird glitch," I thought, and resolved to forget about it.
Last night, AT APPROXIMATELY THE SAME TIME, the same thing happened. No mouse light, I turn on the monitor, and there's the prompt for the power-on password: the computer has once again rebooted, despite the UPS. *And*, when I entered the power-on password, the screen once again filled with messages related to MAC address and DHCP client ... and I had to turn the power off and on to get it to boot normally.
I have checked the event logs, but am not knowledgeable enough to interpret them. I can look for specific messages, if anyone thinks I should.
I have some reasons to have security concerns about this computer, and my work environment. I don't regard myself as a prime target, but it's not impossible or especially unlikely that someone would go to special trouble to try to break in to the box. Still, I would look for other causes first: like a motherboard problem, if anyone thinks I have one.
I unplug the net cable connecting the cable modem to the Internet at night, so -- other than the power cable to the UPS -- there is no other physical link between my computer and the outside world. I don't have a WIFI card. The cable modem -- when plugged in -- is connected to the computer via a Linksys hardware router. (But, the cable to the NET was unplugged both times these mysterious reboots occurred).
I am careful about spyware and anti-viruses, but not zealous. I run Kaspersky AV.
That's all I can think of posting! Help will be much appreciated.