Getting message - Window has encountered a critical error and computer will restart in one minute. Please save any work now. Then restarts again.
That message can also be caused by malware.
Please follow the instructions in this post:
https://forum.avast.com/index.php?topic=53253.0
To stop the shutdown process:
start > run > shutdown /a [enter]
So maybe just a coincidence it started immediately on reboot after upgrading to 2015. Something that the previous version never detected and activated by the update?
Should add that I uninstalled Avast using the cleaner and everything boots up fine. Tried to re-install a few times each time same result. Right now running fine without Avast