OK, after over a year of struggling with the 8935g, I've finally fixed it. I have the Core 2 Duo/HD4670 model, and suffered numerous crashes to solid colours, bluecreens etc while gaming. Most recently in Portal 2 and Dear Esther. I'd taken the laptop completely apart several times, blown out every trace of dust with compressed air, even applied new thermal paste to the GPU heatsinks, all to no avail. I reasoned that it couldn't be temperatures, as the laptop would run extremely hot on certain games without any crashes, and others (eg Portal 2) would crash dramatically to the flashing colours with very little stress.
The solution is simple, and I discovered it almost by accident in a forum post that seemed completely overlooked, #170 here
Download the AMD GPU Clock tool from the following link, disregard the mention of HD5870, it works perfectly well.
AMD GPU Clock Tool v0.9.26.0 For HD 5870 download from Guru3D.com
Install and run.
You'll see the clock speed of the HD4670 (titled Engine) set at 675. Now the original poster recommended lowering this, and while I've confirmed it certainly works, it's not necessary after all. Instead, simply lower the Voltage. Click the drop down menu under the Voltage box, and lower it from 1.2000, to 1.1000. It's a small change, but the result is perfect stability! Just played through all of Dear Esther, an absolutely stunning looking game, maxed out, 4xAA, 4xAnisotropic Filtering, not a single stutter with no problems whatsoever. Portal 2 is the same!
So there you have it, I hope we can put this to rest finally