Blithely, I succumbed to Mac OS X's Software Updates' urgent need to update my old TiBook 800 to OS X 10.3.8. I didn't think much of it at the time and resumed writing. When the update finished, I noticed that the Airport card wasn't connected to the network anymore. I shrugged off the creeping feeling of impending doom and restarted the laptop. Still no WiFi. I couldn't create a network, or manually connect to a network either. In other words, it appeared that the card wasn't functioning.
Apple System Profiler showed the card present, but turned off. This was odd, since the menubar Airport icon showed the card on, but not connected. A brief Googling showed me that I might have wanted to wait on that update. MacFixIt's Troubleshooting Mac OS X 10.3.8 reads like a nightmare. None of the items listed directly pertained to me, however.
I've had this TiBook for 3 years now, and haven't had any problems with it other than a quickly fixed keyboard annoyance and a questionable hard drive. Both issues were quickly remedied by Apple at no charge since the laptop is covered by AppleCare. I certainly haven't had to reinstall the OS through updates from 10.1 to 10.3 and the daily beating that makes up the life of my laptops. It looked like this might be the first time.
Fortunately, it was not to be. I run an Ethernet cable to the TiBook and opened network prefs to ensure that DHCP was configured. When I swapped the Ethernet port to manual addressing, then back to DHCP, the Airport suddenly lit up and connected. I don't know how or why this fixed it, but it did. Otherwise, I've had no problems with 10.3.8 on that laptop. The other Macs in the house have been happy with that update as well, including the Xserve.
The moral of the story is rather obvious -- no matter what OS you're running, reading the release notes and a 5 minute Google is really a necessity.