I upgraded my iBook to Mac OS 10.1.5 this week and somehow lost the ability to put it to sleep by simply closing the lid. It would appear to nod off, but would then spring back to life, and then turn on and off over and over and over again. I found the solution was to reset the power management unit. Everything’s back to normal now.
In other Apple news: I have about 4,000 photos in iPhoto now and find that if I try to delete a lot of photos at the same time, iPhoto hands with a “spinning rainbow” cursor. Forever. I found that if I leave it in the catatonic state for about 20 minutes, and then Force Quit, I can restart iPhoto and the photos are gone as I intended. Certainly not graceful, but it works.