Hey all. My sister's Powerbook is having some very strange issues. At random points, without warning, the computer will go to sleep and then not wake up. Sometimes it will sporadically wake up and then fall back asleep again shortly after, sometimes it will not wake up at all. I have no idea what could cause this except for maybe a messed up battery, but it's plugged into AC power when it happens. So, I'm wondering if something else could be causing this. Any thoughts? Thanks!