I just bought a Powerbook 15" like yours and was experiencing similar problems. Although there was also something wrong with my battery and I had to have it replaced. Firstly, make sure, assuming you are running panther, that you upgrade the system software to system 10.3.2. Apple released a 'battery' upgrade with this verison of Mac OS so make sure you also have that. Both should come up in software update or are on the apple website. Having done that, completely reset your computer not just the power management unit by booting into open firmware (start up the computer while holding down Command(apple key)-Shift-O-F. Once in type in "reset-nvram" and press return then type "reset-all" followed by return
having done this the computer should restart and boot normally into Mac os (the date and clock will be reset). If it doesn't restart type in "shut-down" and the then boto up as normal. After having done this, fully charge the batter to 100% and recalibrate it. This is done by fully charging the batter and then letting it fully drain until the powerbook is forced into sleep mode. This can actually alter the battery life and so it's best to do this as slowly as possible to gain the maximim battery capacity. Do this by first fully charging the battery to 100%, go into the system preferences and into the energy saver preference pane, set the computer so that under batter power it will run under REDUCED processor performance, set it so that it will not sleep and so that the screen will not dim. Then close all network ports (unplug any ethernet cables, TURN AIRPORT OFF) and finally unplug any mice, external drives etc so that nothing is connected to the powerbook, also turn the volume to mute. Unplug the power then, making sure the screen saver is not set to come on, dim the screen right down to black and leave the computer until it goes into sleep. It should take between 6 and 7 hours for it to do this. This should actually be repeated every month. This should sort out the problem. It's worth nothing that mac OS doesn's always let the battery fully charge for some odd reason (to protect the battery agaist power surges or something). If you want, you can check the battery capacity by going into the terminal and typing "ioreg -l | grep IOBatteryInf" it should be about 4400, any lower that 3200 and you should consider contacting apple to have it replaced. If you need any more help, feel free to drop me a PM or an email.
Regards
Rupert
RE: Steven,
Apple has had a lot of trouble with it's quality control lately and it was reported, unofficially, that 3 in 10 of the new powerbooks would have a defect on arrival and that 1 in 50 would be dead on arrival - i just consider myself lucky
