Powerbook G4 sleep/power problems

[dnd912]

Yesterday I had my powerbook running on the battery and all of a sudden when it should have gone to sleep it died. I pressed the power button several times and nothing happened but then plugged it in and it turned back on. When it did power on I saw a gray screen over the desktop with some kind of a progress bar at the bottom. I found this odd because when this happened the battery was at 39%.

Now when I put it to sleep and open it back I get the same thing. Nothing happens when I press the power button but when it's plugged in it powers up just fine.

To make things worse I can't unplug my powerbook's power supply without the computer powering down completely.

I recently added more RAM but haven't had a problem until now. I've tried resetting the PRAM and PMU but I don't think anything has changed.

Someone please help!