Powerbook dies when put to sleep

[Jay Boshara]

I know this isn't an iBook question, but you people are the only ones I know
who might be able to answer it.

My wife's 800 MHz 15" TiBook (running on 10.2.3) has a weird problem.  When
she closes the screen, and thus puts it to sleep, sometimes the computer
will be off when she raises the lid again -- like it just shut down when she
closed the lid.  Any ideas why?  Is there a Powerbook List that might help
me answer this question?