Sager NP8690 Sudden Shutdown

I was playing a game of Garrysmod online on my Sager NP8690 w/ i7 620m and ATI MR 5870, when in the middle of the game the computer instantly shut down as if it were unplugged. I wasn't sure what happened, and I didn't touch anything, then a second later the computer booted without me touching the power button and the same thing happened at the boot screen after about a second. Then the computer booted a third time (without me touching the power button) and this time it actually booted correctly. I was running the laptop without a battery, and had been for some time, but I never uplugged the computer, and even after it died, it the indicator showed that the machine was still plugged in. It appears to be working now, and I unplugged it during use and noticed that it does boot automatically after loosing power. Do I have a screwed up power brick, or is this a sign of a more serious problem? Also this was not an overheating issue (at least not for the CPU or GPU).

 

Update: My computer is booting on randomly now, as long as it is on AC power it boots up after a few minutes.

 

So for a period of time can you check the machine and how it run WITH the battery in? We hope it is not a hardware issue.

If your machine is under warranty exchanging a PSU is not a problem.

Have you tried it running other games?
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Try resetting your bios by taking the MB Battery out for 15min or so. Then put it together and try it again.

A service manual is in the below link

W8xxCU_ESM.zip
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So I'm just tossing stuff out here, but my power button has always been really mushy, and I was concerned that it might break at one point, is there any chance that it's stuck, or randomly triggering? Is that likely? The machine isn't under warranty btw. Also, I put the battery back into the laptop and it's still booting randomly. How do you remove the MB battery?

It's booting and dying as I type this.

 

update: the computer is dead, I can't make it turn on. Even with the battery in on AC power.

 

Many times resetting the bios by removing the CMOS battery on the mother board carefully for about 15 min then putting it back in.

The service manual may not show how to do this however on many models it is underneath the keyboard area when you expose the MB. Look for the little battery they look like the below pic



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Try the above anyway to see if it gets you going, if not some hardware needs replacing most likely.
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Alright, thanks. How much do you think it would it cost to get this computer repaired since it's no longer under warranty?

 

We hope it is not the motherboard that has failed. If it is it is over $300.00 for that fix. Let's hope for the best first. Maybe it is a lessor item.
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Any estimate for the PSU?

 

$90-$100.00 plus the shippng charge.
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