Screen tearing, even when Vsync + TB is on

[meatCake256]

Hi, I'm new here and I registered because I've got a problem with running Amnesia as intended. I'm running Amnesia off Steam and I'm getting screen tearing no matter what configuration I try. I'll try and provide as much info as I can in this thread, to limit the amount of back-and-forth questions because I think others are in a similar position to me. I'd be really grateful if someone could help me out.

Details: I'm running Windows 7 x64 with an ATI Radeon HD 4870, all drivers, patches and updates fully up to date. My monitor runs at 60Hz, at 1680x1050. All unnecessary applications are switched off.

I've tried vsync on and off, and triple buffering on and off, and all combinations therein. I've tried vsync at the software level (as the option in Amnesia itself) and at the driver level, both in ATI Catalyst and in RivaTuner's D3DOverrider, and every combination between the two. I've tried all this with settings turned down, too. Compatibility mode changes nothing, and I run Amnesia as an Administrator.

No matter what I try, I get one of the following:

If Vsync is off completely, I get 60FPS and screen tearing, regardless of triple buffering.
If Vsync is on at the driver level, I get 60FPS and screen tearing.
If Vsync is on at the driver level AND triple buffering is on, I get 60FPS and screen tearing. The tearing is less pronounced but still visibly distracting.
If Vsync is on at the software level only, I get 60FPS and screen tearing, worse than if it were at the driver level.
If Vsync is on at BOTH levels, I get 30FPS, no screen tearing. The game runs very slowly and stutters, regardless of triple buffering.

And by 'screen tearing' I'm referring to the thing where on the screen, the top of the frame doesn't align with the bottom of the frame by a fraction horizontally, in a band that slowly travels up the screen before wrapping around. It's impossible to take a screenshot because it happens while playing, and if you try and take one it'll always turn out perfect because the system will make sure a full frame is on screen before taking the screenshot.

Please let me know if there's anything else I can try. I know my system is supposed to handle this game on High with no glitches or ill effects, and the tearing is really distracting.