I tried again with 100.14.19, and with EDID modes, the 1080i mode is still doubling all the lines, showing the top half of the image filling the entire screen. With all the modelines I've tried, including the ones above, I just get a black screen--they validate, but aren't generating something that my TV will sync to.
There's a reference to nVidia being aware of the problem--that's not the same problem. That was a tearing problem when the mode was displaying. I'm not sure they are clued in to this issue.