Is it possible to get interlaced resolutions working with NVIDIA graphics cards?

I'm using a G-Force2 MX400 and I'm trying to get 1280x960i resolution with 1080i timings working so I can use it with my Mitsubishi HDTV. I've succeeded in getting this resolution to work with Ati cards, but this is my first Nvidia card.

I have installed the 'nvidia' driver as per the instructions on NVidia's website and I've gotten hardware acceleration working. OpenGL screensavers work great, as does Xine video playback.

However, whenever I try to set an interlaced resolution in XF86Config, the log shows the following error:

(II) NVIDIA(0): Not using mode "1280x960" (bad mode clock/interlace/doublescan)

Here's the modeline it's complaining about, which I've used successfully with Ati cards:

ModeLine "1280x960" 55.350 1280 1392 1448 1640 960 1024 1035 1123 interlace +hsync +vsync

Any ideas? Thanks!