Yea I agree with khu, prolly a momentary heat up, or overheat. Remember, if it ain't a crashing, you aint a pushing it. Actually the Mobility drivers have issues.
I've had my 8790 for a little more than a month, and I've gone all over the block. Crashed it running Thief 3, Far Cry, even Doom 3 and WinAMP , and I think that it is all due to poor video code working somewhere. But that's okay, I backed them off and they run great now.
Between the quirky drivers for our Mobility cards which don't seem to be supported by anyone (our first clue to potentially unstable behavior), and the buggy games rushed to market like Thief 3, which has numerous documented problems rendering, it really pushes our boxes to the brink.
Here are my conclusions about my NP8790v:
First rule, I always use the F-10 fan in high-speed whenever I am gaming. Loud noise is a very small price to pay for system stability and component coolness. Why buy a laptop cooler when there is one built in, called a FAN.
Second, I run the Omega Catalyst 4.7 drivers, which are more stable than any others I've tried. I tried the Sager stock ones, the Sager new ones, the ATI new ones and the Omegas. The Omegas run the most stable IMHO. Folks have told me to try the Omegas 4.4 to solve some Thief 3 issues, but I think that I'll wait until 4.8s are out.
Third, since I have the Omega drivers installed I found it very easy to overclock the GPU Core/Memory to 525MHz/290MHz respectively. Got a 20% increase in framerates in Doom3 and Far Cry. Awsome, and runs perfectly stable, with the fans on High. Will not work on battery power though, if you run on the battery, make sure to go back to the stock 405MHz/290MHz specs. When the 8790 switches to battery power, it automatically underclocks the CPU from 3.43MHz to 2.73MHz to conserve power. Not sure if this alone unstabilizes the PC when the GPU is overclocked, or if the GPU doesn't get enough power while on the battery making it prone to bs crash.
Finally, since I installed FRAPS I can tell when the system is really chugging along and when it is bogging down. These games mentioned above are very taxing when turned up to resolutions above 800x600 and I think do not run as smooth as I like them to. SOme folks prefer lots of eye candy to fast performance, but I'm not one of them. When I turn the resolutions up, the FRAPS goes down, and so does the stability. I think that if your FPS is in the teens or 20s, your GPU is getting bogged down and are prone to overheat.
Gee I just wrote an exposition, I didn't mean to. Did I answer your question?