Natx

Hello...
My problem is that when I'm rendering some video (which is like about 1 minute,and about 200-300mb) my computer is shutting down.
This is the second time it's happening but I've rendered many videos before without any problems. Just to mention,my computer isn't shutting down just when I render videos in Sony Vegas but even when I do something else.
I've read that maybe problem is overheating. Could it be possible? Because I'm rendering my videos usually in the evening when my computer already did a lot of things and maybe already has a high temperature. I suspect that problem is in memory because I checked my disk and it has enough space,and I even deleted some of my old projects.
Few minutes ago I downloaded program "SpeedFan" to see what temperature of my computer is, and the highest is about 82.Is it possible that when I'm rendering it,my computer is getting to a higher heat and it reaches it,it's shuting down?
Thanx alot...