First, the mystery hang now looks like it is a severe kernel oops. While fiddling around, I had occasion to shut down the computer. The gnome logoug button did nothing, so I did a 'reboot' in a root window I had open. This eventually came to a grinding halt with the kernel oops.
More fiddling around showed that the gnome logout button did what it was supposed to, but it was unexpectedly slow. Like 180 seconds or something. It is obviously waiting for something to respond or time out, but there is absolutely no clue in any of the logs what is (or is not) going on.
My working theory right now is that these woes are due in some way to the older stick of RAM I put in the computer when I got it. Due to the age of the RAM, it is entirely possible that it is no longer functional. I'll have to take the computer apart to see what kind of mainboard it has, and then look up on the net what kind of memory it can/should take. Then I'll just buy some of that.
Then I lost most of the morning to a power failure.
Turns out that the Sun has a higher draw on the UPS than the PII/350 does. The PII would run for about ten or fifteen minutes, while the Sun dies after about five.
I think we need some kind of UPS for the PII and the switch, cable modem, and router. It could be a long summer, and this outage shows that not much has changed since last year.
This power failure happened around 10 in the morning, and everything was still down when I left for lunch. Backtracking from the clocks, it looks like everything came back on about 1 in the afternoon.