I have an ASUS g50vt-x5. Not the worlds best laptop, but the game in question I'm trying to play is F.E.A.R. (also not too graphic heavy)
My laptop runs the game is perfectly on max settings, 75% of the time I'd say. But even if I reduce the settings to the absolute minimum, I get the same problem. I'll be playing for anywhere between 5-20 minutes, and the framerate drops ridiculously low. I'd say anywhere in the 5 fps region. Unplayable. Sometimes doing a Quickload fixes the problem, sometimes i need to quicksave and reload the entire game to fix it.
First I thought it was just bad hardware, but no, when it reloads the same scene with the same everything, it runs fine. Then I thought it was my video card being 'throttled' due to excess heat. Also not the problem, it remains a lot cooler than usual even during the lag spikes.
So I'm guessing it's a RAM issue? I did a fresh install of Windows 7, so I don't have programs eating away at my RAM, but even before W7 when I had Vista, I couldn't even play the original Halo without this issue, which is even lower quality than FEAR. Even when trying to run The Incredible Machine, it said I needed 32mb of ram to play and I didn't have enough to run it. Something is screwy and I don't know how fix this issue. Please help or ask for more info if I didn't give it.
EDIT: I also have the newest Nvidia drivers, I forgot to mention that.
This sounds like overheating, This is why there are very little laptop gamers. Anyways the 9800M should have no trouble playing F.E.A.R at the right temperatures, What I advice you go ahead and buy a laptop cooler.