When I returned, it wouldn't hold a charge for more than an hour -- macthud suggested installing some updates, which I did, and helped for a while, but now... -- now I can't get it to go for more than about 30 minutes, even on a full charge, AND it doesn't warn me before going to sleep, which it seems to do at times not particularly related to actually being close to being out of charge.
Is this a battery problem? Or a software problem? Will buying a new battery solve the problem? Or something else?