Faint horizontal line when in dual mode?

I have a 622 connected to my 30" Philips HDTV via component cables. My TV does not have any HDMI connection. I keep the 622 in dual mode and have TV2 connected to the RF output. I noticed that when TV2 is turned on, that I can see a 1" horizontal line on my HDTV. It is very faint and it slowly (30 minutes) rolls from top to bottom. I mainly see it when watching dark scenes. The line is about 2 shades lighter than the rest of the screen. If I turn off TV2 it goes away. I also see the line on TV2 in my bedroom. That rules out my HDTV as the problem. Can this be a bad 622 or should I maybe change the channels of my RF output?

That is interesting. How would I determine if this is the problem? I have the TV2 output connected to a 4-way splitter that feeds all of the other TV's in my house.