Paikea: You need to enable Vsync to fix the "warbly" line. Technically it is screen tearing. Get a program like D3doverrider that comes packaged with rivatuner and enable both vsync and triple buffering. That will fix the "warbly" line. Or if you are using Windows 7 with Aero, play in windowed mode which automatically vsyncs games. I don't recommend that option tho as it seems to make games run slower. I disabled aero altogether now I force through d3doverrider. Keep in mind you will see probably significant slow downs unless you also enable triple buffering, but triple buffering takes alot of vram so you may see reduced framerates especially in towns, but nothing major and most likely never under 30 fps.

I also have a 5870 and I can play with 1920x1080, 9/4, 4xMSAA, High/Highest and get 60 FPS in the field, 30 fps in towns. Before the triple buffering/vsync it was 60 fps but way less, like 27 in fields. After triple buffering it flip-flopped, now I get 60 fps in fields where it matters but 30-60 fps in towns depending on which part of town. Certain parts of towns seem to use more VRAM so I get lower fps there. Go figure.