Overheating? Problem -- Requesting Help

I have an Acer 7741G-6426, which is an i5, with an ATI 6550M gfx card. I upgraded to 8 gigs of RAM.

I'm getting random shutdowns, but I can't determine why.

I've tried cleaning it out, and that seems ok. I even had it swapped out completely, and that didn't help.

I've run diagnostics software on the RAM, harddrive, cpu, and it came back with no problems.

Here's the issue. It clearly wants to auto-reboot more often when gaming, however, it has happened randomly when almost under no load at all (though this is very rare).

Now, that makes sense, of course, except I don't show the temperatures anywhere in the range of it being a forced shutdown.

I just tested it while running Star Wars: The Old Republic. Frame rate was 30-60, with all settings at minimum, and it ran pretty smooth. The gpu temp hit a peak of about 67 C, and the CPU was right about the same for a peak temp (one core peaked at 67, one at 64). The bottom of the case was hot, clearly, but it was elevated on a cooling pad. The fan air was quite hot, but the fan wasn't as loud as one might expect. I read the cpu isn't supposed to shut down until 105, and while I'm not sure about the gfx limiter, I'd imagine it's well above 67.

Now, I tried this 3 times. Twice it auto-restarted the computer within 2-3 minutes of play. The third time it ran for about 20 minutes with no crash, and I shut it down myself, to come here and ask for advice. The first time was on battery only, the second two tests were plugged in.

Any idea about what's going on here?

Thank you very much!