So, I sent my 360 to Microsoft in March due to a RRoD. I received a replacement unit sometime in April. Since then, I have noticed faint white vertical lines appearing, mostly on dark backgrounds. I'm connected via HDMI to a Samsung HP-T5044 plasma panel. This problem never occurred until I got my replacement from Microsoft. I don't have anything else to connect to the tv via HDMI, but all of my other inputs are line-free.

Is the GPU damaged or what? Anyone else have a similar problem?