Horizontal Tearing Using Nvidia Drivers and LCD

[HeavlyArmdPokey]

Hello. I seem to have a very odd problem, because hours of googling turns up nothing. You see, I have two LCDs - a BenQ FP93G-X 19" and a Soyo Topaz S 24". I'm running an 8800GTX with nvidia-drivers 169.09 and gentoo-sources 2.6.23-r3. The problem I'm about to describe has always existed, however.

Soyo 24" LCD
BenQ 19" LCD
My xorg.conf - At the moment the 24" is disabled

The monitors are very nice and have worked well, except for one thing - the 19" has a peculiar little line that runs down the screen. To illustrate, here's a picture:

Odd tearing

Sorry about the quality of the picture. If you can't tell, I'm dragging the nvidia-settings window back and forth horizontally. The bottom half is lagging behind the top half. The inexplicable thing is that the "tearing line" slowly moves down the screen, and when it hits the bottom, it starts back up at the top again. Everywhere else is smooth sailing. It's almost as if the refresh rate is a Hz off or something.

I've tried many things to remedy this problem; I have spent many fruitless hours experimenting with custom modelines. Previously, I solved the problem with Compiz-Fusion and vsync, but I have since decided to cut the eye candy, and I now have to deal with this again. Any help would be greatly appreciated.

[PaulBredbury]

Speculating wildly: I don't think that a single video card can synchronize *two* displays. So the second display has some annoying "artifacts", since it is synchronized with the first display, which means that it is not quite right.

[HeavlyArmdPokey]