Why does my MBP say it was restarted "because of a problem"? Since upgrading my MBP from Lion to Mountain Lion, every time I restart (planned restart, with nothing abnormal - I even close all applications before selecting Restart), my MacBook briefly shows the message "Your computer restarted because of a problem" when booting. Then, once I've logged in, I also see a dialog that says "Your computer was restarted because of a problem". As far as I know, there is no problem; everything seems to be working normally.

How can I begin to diagnose or get rid this? It's merely a cosmetic issue, I think, but it is annoying. I have read this Apple support document, but that only seems to be relevant in the scenario where the Mac crashed because of a kernel panic. As far as I know, mine didn't.
I had the same annoying issue on OSX Mavericks (10.9.2), and resetting the NVRAM / PRAM as per Andrew Ferrier's answer didn't resolve it.

Instead, I opened a Terminal window and found a week old Kernel .panic file in /Library/Logs/DiagnosticReports/

I simply renamed it to .panic.old with the following command:

sudo mv Kernel_[rest_of_filename].panic Kernel_[rest_of_filename].panic.old


After a reboot I no longer get the annoying message!