If you're getting vertical lines on the tv, you might want to check to be sure that you're not in progressive mode on your hdtv. If you have an HDTV (as you said) then it most likely operates in several modes -- 480i (interlaced, regular tv), 480p (progressive -- available from some digital broadcasts and from a progressive scan dvd player), and then hi def modes like 1080i or similar.

If you're getting vertical lines, your tv may be set to progressive while the signal you're receiving is interlaced, causing vertical lines and flutter in the picture. Play with the menus on your tv -- most likely the 'setup' or 'advanced' menu, and see if you can get to a point where you can select the video output. I had a similar problem with my Mitsubishi HDTV and this was the adjustment that solved it.

Hope this info helps...

-- Kevin