You can see it start as soon as XBMC loads. The video doesnt quite do justice to how bad it looks in person.
I'm pretty much at a loss here. I have 3 HDTV's that I've tested this on, one a 720p native LCD, one a 1080i native plasma, and the last one a 1080p native plasma. The xbox is hooked up with an ebay R/G/B component cable. On the 720p and 1080p native TV's, I have no problems whatsoever. On the 1080i TV, I get the interference lines as soon as XBMC (or essentially any program on the xbox with an HD signal) starts up. I have tested this on all video modes available in XBMC (480p/720p/1080i) and the lines show up on all of the HD settings. If I set XBMC to output on one of the SD modes with the component cable it's fine; it's only when it's outputting an HD signal that I get the lines.
The first thing I noticed is that I could affect the interference lines by moving cables behind the TV across one another. So for my first test I unhooked everything near the TV and moved it out of the room. Still have the lines with only the xbox hooked up to the TV. I also had both the TV and xbox hooked up directly to the wall outlet just incase it was my surge protector acting up (it wasnt).
The 1080i TV has 2 component-in's, both of which suffer from the interference lines. However, I didn't have a problem with interference whatsoever with the other component devices that are normally hooked up (cable box/Xbox 360). It's only with this particular xbox component cable that I get the lines. The only thing that has me stumped is that the exact same cable will work perfectly fine on 2 other TV's.
I'm tempted to just buy another component cable but I don't see it being an issue since it works fine on my other TV's. I also can't see it being an issue with the TV since my other component cable devices work perfectly fine on it.
Like I said, I'm stumped. Any ideas?