Comment 7 for bug 116826

I have the same problem.
If I put the computer to sleep for a short period of time, it wakes up fine. If it goes to sleep due to inactivity, first it wakes up properly. I can even open an application of I'm fast enough. I get a message saying that it failed to hibernate. Then it proceeds to hibernate on its own after about 20 seconds of waking up from sleep. After I turn the PC back on, it un-hibernates fine.