About CPU temperature: PC crashed at 45C and 30C as well, so I'd eliminate this issue.
You are right, I did not think that your current problem was a temperature issue, just that your temperatures seemed a little on the high side. With temperature issues you tend to get more consistency? it should cut out after a certain period of time.

I am not convinced that it is an attack either. As I suggested, what is the motive?

I am inclined to suspect some sort of applications/services conflict.

Please try disabling all power saving, all automatic updates and any services and applications that you do not immediately need. This seems to be a by chance occurrence, so it is the check for update software that I suspect is conflicting with something that runs normally? or two update routines are trying to use the same resource?

At this time I would probably install a simple firewall like ZoneAlarm, and authorise nothing. It will then ask for permission for things to connect to the internet and I would catch the culprit. I am sure that you can get a 30 day trial?

Good luck!