Same problem this morning, except I had done no upgrade. I hadn't installed or updated anything for a few weeks. Just started it up this morning with the spinning circles. I read everything I could (using my CHROMEBOOK!) with no answers. But I noticed that the system would go into standby when I used the standby key.. And I noticed that it even went into standby itself after 20 minutes. I could even shut the system down using the power button but when powering back up it went back into the spinning circles. no other keys worked, other than the standby key. Big problem is that I had neglected to make a recovery drive. So I thought I'd try something, knowing that sometimes if the power is cut off sometimes the system will bring up the safe mode option. So I pulled the plug on the computer and then powered up. It then booted up as if nothing had happened. I am know making a recovery drive as I type!