Scott: if the problem is what I think it is (the white line thing) the problem lies in what I said before, the hardware of the video card is causing issues with the cable. I have seen some cards act FINE while others are horriable. You could try and swap the Nvidia card for a ATI card (Preferably a AIW, but even normal ATI Has better TV-out) Another thing you could try would be to buy a stand alone TV-Card that supports TVout of your desktop. However if it is something different from that please PM me and I will be happy to help as much as I can. Finally the RGB inputs are for a HDTV input, so I think using those is out of the question unless you got yourself a HDTV-ready Reciever.
DrJekyll: The shuttle case is a Small form factor case that is about the size of 1/4 of a normal Full tower case. There VERY small and will fit almost anywhere. The only problem with them is that the heat issues are quite high. You can find reviews on most of the good review sites. Such as:
http://www.tomshardware.com
http://www.anandtech.com
http://www.sharkyextreme.com
http://www.hardocp.com
those are just a few.