Sometime this week my G4 PowerBook started acting up. It would go to sleep spontaneously, and sometimes when I "woke" it up it would go right back to sleep. It started happening around the same time I applied an OS X update, so I feared that that was the culprit. Then a co-worker sent me this Apple article which describes how to reset the Power Management Unit (PMU). It was such an easy procedure that I immediately gave it a try even though I was in the middle of several things...these narcoleptic episodes were hurting my productivity. So I powered down, removed the battery, held down the power button for 5 seconds (mississippicized of course) then I popped the battery back in and booted up. That was about 7 hours ago and so far so good.