Computer shuts off/restards randomly when playing one game

Ok this problem is not as easy to diagnose as it would seem, to me anyway. I'll put it in bulletin form.
1. Randomly my computer shuts off/restards when playing League of Legends.
2. It has not happened when playing any other game, even games that take more resources to play. (I haven't tested this enough for it to be foolproof though)
3. Sometimes I'll go for 3 days without the error happening, other times it will do it so often I cant even load the launcher before my computer crashes.
4. It has only given me a blue screen once out of about 30 crashes and that screen only flashed for a solid second.
5. I have monitored my video card(which is only 4 months old, 9400 gt) and the heat doesn't go past 65 celcius while playing games. At idle its about 40.
6. My power supply shouldn't be the issue because I've used a 9600 gt for a year before it broke (not sure what the cause was though).
7. I sent my computer through the 3Dmarks stress test simulation and it doesn't crash.
8. I downloaded Everest and ran it while playing and everything looks the same as my brothers computer which is identical to mine(keep in mind I'm not entirely sure what most of the stuff on this program means).
9. I've scanned my computer for virus's and even ran combofix at one point which turned up nothing.
10. I use a wireless-g linksys router. Both my brother and I use the same adapter type. When my computer goes to crash i'll have a few short lag spikes for about 5-6 seconds then my screen goes black and my computer shuts off or restarts.
11. I had an extra adapter of the same type that I switched out and the error still happens.
12. I defragmented my comp a few days ago.
13. I tried system restore to an area before it started happening.
14. I updated my video card drivers to the latest ones.

My only lead so far is the 1 second flashing blue screen which all I could read said driver. Having upgraded my video card drivers leaves me clueless though.
I have not upgraded my wireless-g adapter drivers in some time (if mine are even still supported as I don't know if I can find any upgrades, could that be the issue)?




The only thing I can think of that I haven't done is reformat.

 

you can disable a restart after the error, so you can get the blue screen code.
you didn't specify which OS you are using, for xp:

1. Right-click My Computer, and then click Properties.
2. Click the Advanced tab.
3. Under Startup and Recovery, click Settings to open the Startup and Recovery dialog box.
4. Clear the Automatically restart check box, and click OK the necessary number of times.
5. Restart your computer for the settings to take effect.



Since you said you changed video cards in the past, you might want to properly uninstall any drivers, and reinstall new ones using Driver Sweeper.
http://majorgeeks.com/Driver_Sweeper_d6171.html
Run the program to remove any nvidia related display drivers. Reboot, run it again just to be sure, reboot, then reinstall the new drivers.

 

My bad was tyring to think of things I left out for started I have couple.
1. I uninstalled and reinstalled the game
2. Im running on vista 32-bit home edition.

The drivers for my old video card were the exact same (both 9xxxx GeForce cards)

Is there any chance that still has an affect?

As for the restart/shut off my computer turns on normally acting like no error occurred. Only one time did it give me a blue screen, barely flashing, and I can't seem to get it replicated.

appreciate the help regardless.

 

i had the same problem. i played a video off the internet or my wife would play a game on facebook and the CPU shut off by itself, like someone pulled the plug. I searched a little on the internet for what could be the problem and found a solution. I opened the tower and dusted the hell out of it. That was it. I plugged it back in and immediately noticed that the fan speed was quiet again and the cpu ran like a champ, good luck with your problem...

 

Have you run Memcheck through your system yet?
http://www.memtest.org/
Burn and boot off that and see if it makes a few passes clear.