Got to disable Geforce Experience. Cursor-locking works now, but 1280x1024 is still very blurry.
Printable View
Just for your info: my game looks like shit if i double click on the windowed version by mistake. It rescales the window into the tiny bit it needs to completely fit my screen.
If you, for some reason, have a tool that autoscales it to fit your screen it would explain it maybe.
To describe that screen: it looks like there are lines in both directions. The lines have the color lf whats on my diabloscreen, but its drag'd... hard to explain with my english knowledge :P i can make a screen later if im home to check if our issue is the same. If we know the issue, we may find the cause and a fix
Lucid is pretty close to the issue, those lines appear when the screen size is not what it is supposed to be, which usually happens when someone isn't using Direct2D, if you have another program that latches onto games (Like your Geforce Experience was) it may be causing the problem.