Quote Originally Posted by Martok
Well now I have two new problems.

Actually, the first problem never went away: My computer is still restarting without my telling it to, even though I unchecked the "Automatically restart" option on My Computer.

In addition, this time Mozilla failed to restore the internet sessions I'd had up when my PC restarted.
Firstly, clean out the inside of your computer, as you may have a problem with ventilation and cooling.

Secondly, try the session manager add-on.