I can see from this page in the mythtv wiki:

http://www.mythtv.org/wiki/index.php/ATI_HDTV_Wonder

That the NTSC input on this card is not supported. I am just wondering if that is still true? Is there any workaround, or updates that would allow the NTSC portion of the card to work? Is there a reason why the NTSC is not supported? Any plans on getting this supported?

When I tried to use it, I actually got the NTSC video to work for about a half a second whenever I change the channel, its kind of a tease.