wierd gfx card problem when playing game

my Nvidia card constantly stopped working and switched to integrated card for about 1 minute then switched back when im playing MW3 , it always happens after 30mins playing then again in every 10 minutes . its really annoying , i have tried upgrade gfx card driver , set use nvidia processer in both global setting and mw3 in Control panel ,none of them working . firstly i thought it was MW3 's problem ,then i tried in World of warcraft it still happens but not that frequent as in MW3 . any1 know whats wrong with my card? many thxs
my alienware r3 spec : core i7 2630QM 2.00ghz ,8gram , nvidia geforce gtx560m 1.5g

 

I was having issues with my 580m. Some programs weren't switching when it should. I ended up flashing the modded A08 BIOS and disabling the integrated graphics. Ever since then I've had no issues. Granted my battery life has shortened, but I use it plugged in 90% of the time, so that wasn't an issue.

 

is that the only way to fix this problem?

 

You could try and delete your graphics drivers, reboot into safe mode and run ccleaner, then reboot and do a clean install of your video drivers.

 

just noticed my motherbroad temperature is 90c+ when playing game , and 70c idle， is this normal?

 

Not sure what you mean by motherboard temperature; perhaps you're referring to your GPU and/or CPU?. In any case, if you're getting temps as high as that (70C idle especially), something's wrong. To see if there's anything wrong with the fans, download HWiNFO and use the fan control feature to see if that helps; more info here: Alienware Fan Control. However it's likely you'll need to repaste your GPU and CPU. There are guides here on the forums. Give me a sec and I'll dig those up.

edit: here you go: M17x-R3 CPU & GPU Re-Pasting Guide w/Pics!

 

thxs for the reply , i meant the NorthBridge temperature .

 

Hmm...I'm not too familiar with this but AFAIK, the northbridge functions on all Sandy Bridge processors are performed on the CPU. So I don't think there's a separate northbridge. Someone more knowledgeable in this aspect may correct me but I believe your CPU may be overheating due to one or more of several reasons including bad paste job, dirty heatsink, broken fan/disconnected fan, etc.
You GPU may be overheating as well. What are the temps on the GPU?

Out of curiosity, what monitoring program are you using?

 

its called 360 Safeguard, my gpu was around 65c and cpu around 60c when playing game .