Nothing to worry about, my iBook normally stops at 99%, and sometimes even 98% or 97%, it's quite normal, and there has been an article about this on Apples support pages (don't have link - too lazy to search). Has something to do with calibration of the battery and the fact that it will not start recharging berfore it dips below 95%... the main point: Don't Panic! (Well, the premiere is closing in on us.)