I have a white powerbook about two and half years old. I experienced an odd problem recently that has me baffled. I occasionally pull my power plug out to let the Mac work off its battery. I do this from time to time when not traveling until I get the usual screen prompt 'battery low' and then plug in again to recharge. The battery has had only 144 recycles, and SymPro seems happy with its condition, calling it Good. It is not a Sony battery which I have read is causing some problems. But now even with the battery fully charged according to SymPro, I am unable to work off the battery. After only a short period of unplugged use, the machine will completely and unexpectedly shut down without any warning at all. So for the moment, no travel computing. Any thoughts or ideas appreciated.