Ever since I installed my OPUS for my 3.06 P4 shuttle I have moving horizontal interference lines in the video. What's interesting is that these lines seem to become more prevelant when the PC is accessing the hard drive. For example, when you hear the drive clicking away, the lines get worse.
I have the 12V remote wire run near the VGA cable. I know this is far from ideal but when I did it I didn't think about this type of thing.
I tested the video quality of the cable alone with no current flowing through the remote wire with my laptop. However, this of course is without the CarPC being on.