For the past couple weeks, the fan of my iBook would start to make a relatively loud whirring sound after a fairly short duration of use; this sound had occurred before, but I had blamed it on poor ventilation (it would be on my lap while I sat on the couch). After looking at some Apple discussion forums, I realized that others were having the same problem and it wasn't that big of a deal.
Then, yesterday extremely erratic lines and colors started to appear on the screen. They would intensify, and then basically freeze the screen, so that nothing was visible. I restarted, and after a disk check, it booted properly. And then it happened again, about 10 minutes later.
Out of about 6 or 7 unsuccessful reboots, we were finally able to get into the system. We backed up my essential data to Ben's computer, then Ben called AppleCare. At that point, I was not in the mood to speak with customer support since I have some sort of irrational opinion that things like this shouldn't happen. They told him to remove the third-party RAM (he did). Didn't help. Then they told him to remove the battery and adapter, and reset the "power manager". Then they tried resetting the PRAM, which didn't work (it only restarted twice, whereas it was supposed to reset as long as the keys were pressed). Then they tried to boot into Open Firmware, but the screen stayed black. We tried booting normally, and the screen came on, but the lines appeared almost right away now, and moving the screen on its hinges didn't help. Overall, the customer support person was as helpful as he could possibly be.
They concluded that it was a problem with the logic board (maybe Video RAM) or the cable that attaches the logic board to the LCD, which sometimes comes loose, particularly on laptops or other computers where the monitor moves around (like the LCD iMacs).
So, they're sending me a box to ship the iBook to Houston for repairs and I'm back on my desktop -- which thankfully, has most of the current applications that I've been using on my iBook (Chimera, NetNewsWire, Photoshop 7), and more importantly Jaguar. After importing my mailboxes, I wasn't really up to installing a slew of applications.
So what went wrong? I'm not quite sure. I know that the whirring began after I installed Jaguar. Perhaps Quartz Extreme and the increased use of my graphic card caused the fan to work overtime, and something got shifted when I would nudge the computer to stop whirring. Note that I never shook the computer -- I would just press a bit on the bottom of the case and it would stop.