Mobility 5850 - 3D games freezing, with brightness stuck

Since last Monday, my laptop's been through its fourth at Knowhow's facilities. I was anxious to play games like Euro Truck Simulator 2 and Gmod again, but after a minute or two of gameplay, they would both freeze. From there the screen would turn black, turn back on at full brightness, and allow me to play for a few seconds before looping the process again. The only way I could stop this was by 'Alt-F4'-ing my way out of the game, which would allow me to change my brightness.

At first, I tried updating the drivers as that could have helped, though, instead, made no difference. From there, I proceeded to do an 'express' uninstall of the drivers and anything else associated, restarted, installed the driver only, and restarted again. No success. I even tried Red Faction: Guerilla, only to be met with the same results. Weirdly, though, 2D games like Hexcells, Prison Architect and Speedrunners run flawlessly!

I'm using the 14.12 Omega drivers, according to the Raptr app.

Does the audio become choppy or stutter while the screen is dark? Also, do you notice any abnormal heat or sudden fan surge from your laptop?

Each time I tried, the audio would go on for a few seconds after freezing, before stuttering itself. I've tried switching back to onboard audio - I use the Xonar U3 as my sound card - but to no avail. Heat and fans, however, just ramp up after a minute or two like they've always done.

I have managed to compile a dump 'zip' file with what I found from the Reliability Monitor, so that may help matters a bit.