7800gtx antialiasing problem

Hi, i have a little problem with my videocard. It's an asus 7800gtx (not
o/c). Drivers version 81.95. Motherboard is an intel 955.

In some games i've noticed a line just a pixel wide on top and left of the
screen that is incorrectly displayed. I don't know how to explain it so i've
included some captures.

It only happens with antialiasing enabled. Captures only differ in that
thing. Correctly displayed = aa off. Strange line on top and left = aa on.

I've tested it with different drivers and configurations with same result. I
also have played a little with rivatuner but no result.
It seems to happen only in some direct3d games, games based on opengl like
quake 4 and doom 3 or call of duty are not affected.

Captures are enlarged top left corners

NFS most wanted aa on

http://img380.imageshack.us/my.php?image=nfson1ks.jpg

NFS most wanted aa off

http://img530.imageshack.us/my.php?image=nfsoff6ot.jpg

Dawn of war aa on

http://img232.imageshack.us/my.php?image=dowon3or.jpg

Dawn of war aa off

http://img232.imageshack.us/my.php?image=dowoff2et.jpg

These are just two examples, it happens in more games like gta san andreas,
nhl06,...
Has anybody noticed these lines or do i have a problem with drivers or a
defective card?
I'd appreciate if anybody can check this out with his videocard.
It can be better noticed with enlarged captures.

Thanks for your help