This 9F Error is caused due to Driver Conflict or the Virus Infection. Many times it gets solved when you repair your OS. So I would like to suggest you to Repair your operating system.
It seems unable to handle a power state transition and it's behaving as if the machine is in power state "X" when it's really in state "Y". It's possible that the underlying hardware (the drivers in your machine?) is the real culprit, and its driver is merely the conduit for bad news, but it's more likely that the driver is buggy. Suggestions:
- Try updating that driver to the latest version, then test what happens when you leave the laptop to sit idle again (thus triggering power state transitions).
- If an update doesn't help, try removing the driver outright and testing once more. That's not a solution but at least you'll know for sure whether it happens with the driver gone.