Over the weekend, my 12" PowerBook G4 was involved in an incident that, I thought, spelled certain doom for my all-time-favorite Apple laptop. I was using the machine with it perched on my knees, and happened to be applying the Safari software update when disaster struck. The update was at that point where the OS has shut down and the progress bar is marching across the screen. Just then, our youngest child came sneaking up on me and applied a running hug-tackle (I was on the sofa at the time, but hug-tackles can happen anywhere). At impact, the PowerBook flew off my knee and landed on the back right corner on the (thankfully) carpeted floor. When the machine hit the floor, it instantly kernel panicked, and I thought "well, that couldn't have happened at a worse time."
When I tried to boot it, I got a chime, but nothing else. Every trick I tried, including booting from a CD and setting it up in FireWire target disk mode, failed. Then I tried resetting PRAM, which also didn't work...but it did boot the machine into Open Firmware, so I knew the machine was functional at the lowest level. Typing mac-boot at that point, however, resulted in a scary-sounding error: ALLOC-MEM request too big!. From the sound of it, I thought maybe it was something with the RAM, but I wasn't sure. A quick trip to Google on another Mac found the answer to my problem in this blog post.
It turns out that (at least on this PowerBook, and probably others) the ALLOC-MEM too big! error is caused by a loose AirPort card. You can find instructions on reseating AirPort cards for various PowerBooks in this article on Apple's support site, and the linked blog post contains photos of the process.
After pulling and reseating the AirPort card, my PowerBook G4 started right up just as if nothing had happened -- hooray!
Mac OS X Hints
http://hints.macworld.com/article.php?story=20081114203923522