A few days ago I got Tiger freezing up, repeatably … I finally found a workaround.
Running Tiger 10.4.1, I added some large pictures to my screen saver, and updated to the latest QuickTime. Then I found Tiger freezing in all circumstances after 10 to 15 minutes of use. Lots of reboot. Unhappy Mac user.

Workaround: I finally found (using Jaguar) some hints that QuickTime 7.0.1 might have some freeze bugs. I rebooted into Tiger, then quickly changed the Screen Saver and Desktop not to change pictures. I suspect that doing so invokes QuickTime’s fatal freezing flaw.

Tiger has once again given stable performance, no longer freezing up.