Recently moved up to 9.1 from 9.04. Wallstreet PBook.
Couple of times recently have tried to wake it from sleep and it gets halfway through waking up - then decides not to and goes back to sleep. One can play the game for hours, but eventually it needs a warm reboot.
Nothing unusual extension-wise - and in particular, nothing that wasn't there before the upgrade (it's actually a dual-boot system, with 9.0.4 on another partition.)
I don't have X installed. I did do the battery update ages ago when that was an issue. The battery is charged (4 lights). It was plugged in to the mains.
Clues? Ideas? You can also email me - email@example.com.