Hi Doug,
The standard drill for this sort of odd behavior is to back up your data then:
1) Reset the power management system: http://support.apple.com/kb/HT3964
2) Reset the PRAM/NVRAM: http://support.apple.com/kb/HT1379
3) Boot into single user mode: http://support.apple.com/kb/HT1492
4a) Run fsck (instructions will be above the prompt) if you don't have AppleJack installed
4b) Run AppleJack
If this doesn't return your Powerbook back to normal operation, then I suspect you might have a hardware issue (battery or logic board)
Hope this helps!