Is this caused by low battery? I have an Asus UX31A, and I left it unattended. As usual, in 5 minutes, it went to sleep mode with the lid still open. I came back a couple hours later, and I noticed the laptop was off. I was still able to turn it on by manually pressing the power button (battery was at 2% though), but I don't understand why it shut off. If it was in sleep mode and the battery was near depletion, then wouldn't that result in a "Windows has recovered from an unexpected shutdown" upon boot? Does Windows have a mechanism to wake from sleep from a super critical battery level to shut down all programs and power down the system completely? I noticed that upon booting, firefox didn't give a fit about improper shutdown.
Here are my power settings btw,
powercfg -h off has been ran, so hibernation is off. And here is the event log: http://www.mediafire.com/download.php?lbfhl21g0nj2adi