Horizontal line across the screen (tearing?)

[Wtr]

I'm trying to play Amnesia with a Radeon HD 6770 GPU, but there is a blurry horizontal line creeping up and down the screen whenever I walk or look around. I'm guessing this is a screen tearing issue and has to do with the monitor's refresh rate?

Turning v-sync on and off does nothing, nor does forcing v-sync through the Catalyst Control Center and D3DOverrider help.

Specs are as follows:

HP Pavilion dv6 Notebook PC
Intel Core i7-2670QM
8 GB RAM
Radeon HD 6770
Windows 7 64bit

Running the game in windowed mode seems to be the only graphics option that fixes this, but as a result the framerate takes a significant hit. I hope someone can help me with this, as it renders the game pretty much unplayable.


Thanks.