Joel Barriere's Onyx troubleshooting utility for OS X is free. It comes well recommended, so when my main machine was misbehaving I tried it again.
This time the Onyx startup test told me I had a drive directory structure problem. I was a bit surprised; It's been years since I ran into something like that. Onyx recommended I run disk utility from my 10.6.2 installer disk.
I was lazy, so I tried safe boot instead. Safe boot won't work with a wireless kb, so I plugged in a wired kb and held the shift key down on restart. Surprised again -- it didn't work! I thought safe boot would run fdisk if it found an error, but I guess not.
So I gave in, found my OS X installer disk, and ran Disk Utility from there. It found a missing directory item and fixed it. The behavior has changed over the years, now if Disk utiliy fixes an error it runs a second time to look for uncovered problems. It was fine, but I ran it a third time because I'm that kind of geek.
I don't know if this had any relationship to my problems. My iMac's screensaver uses images hosted on a Time Capsule external share; for some reason it's been dropping the wireless share and failing to reconnect. This is a pain to debug, because there could be multiple causes and because, even at the best of times, OS X doesn't recover from dropped shares very well.
Still, I'm glad to have found something fixable. I made a donation to Titanium Software. I meant to give $10, but I didn't pay attention to the denomination so I gave 10 Euro (about $13 or so).
I wonder if Onyx will be sold in the OS X App store come January. Since it's always been donation-ware (free) that would probably cause some complaints, but this is a venerable and well regarded utility. Barriere surely deserves some revenue.