In which a little blip takes a couple of days to recover from, and a once forgotten important lesson is remembered. Forcefully.
A while ago Apple released an update to OS X - to version 10.4.8 - which I didn't bother with. But then a new version of the firmware for the MacBook came out a couple of weeks ago, and while bringing it down I downloaded and installed the OS update.
And then the wireless networking died.
Well, didn't die exactly, but every 30 to 60 seconds AirPort would deselect the network, and I;d have to go to the menu and manually select it again. 30 to 60 seconds later, the same again. Apple support were no help as I was outside the 90 days complimentary phone support, and given an allergy to extended warranties I haven't bought AppleCare. Instead they suggested I take the machine to my nearest Apple-approved Service Centre. On the other side of town.
Since this was Friday anyway I thought I'd try a couple of things over the weekend. Cue a re-install, and then a tracking-down of the previous OS update. Now I'm sitting on version 10.4.7 of OS X, and all is well. Still haven't fully rebuilt my environment, but I'm considering running the ..8 upgrade again to verify that was the problem.
The important lesson? Before running an upgrade, especially an OS-type upgrade, take a clone of your system. It makes for a much easier rollback.