So this is a problem for 1080i and any other interlaced resolution you might create in Crimson or CRU.
Basically, instead of displaying the full frame, Windows will cut the bottom half off the frame, the stretch the entire top half to fill your monitor. I haven't tested this on a flat-panel monitor but this is what it's doing on my CRT.
Major issue, because interlaced resolutions are great when you want to run double vsync at a refresh rate/resolution where you'd normally be bandwidth-limited. Say 2560x1600 at a flicker free 100hz in progressive would be a 455mHz pixel clock (too high for VGA and DVI connections), but in interlaced it's only 228mHz. With double vsync this makes a very smooth 50fps experience. Just as one example.