Please make sure its not something completely stupid like light shinning thru the blinds onto the tv....
That happened to me with my XBR3. I noticed a very similar line and I couldn't figure out what it was. I turned the lights on, turned them off, I switched inputs, I turned the TV off and on, still had the lines. Then, since it was dark I opened the blinds to change out an HDMI cable and away went the line
I know its silly, but it freaked me out for almost 45min.
So.......I've never really had a problem with my XBR3. If you really do have a problem with it then you've got great luck..... or bad luck, however you want to look at it.