Strange garbled display - Nvidia 7900GS & D-Series JVC *REVISED* *FIXED*

[phildo77]

The problem I'm having goes like this:
1) Run mame game (or start Game ex)
2) Game plays and looks fine (or Game Ex sits there) for 15 or so seconds
3) Screen goes garbled (almost looks like a sync issue but I don't think its the TV, I think its the vid card)

Info:
-Windows XP
-Nvidia GeForce 7800GT (latest Drivers)  Nvidia 7900GS series (latest drivers)
-I'm not sure of the model of the TV, It says D-Series in the top left corner of the front of the frame.  I think its a JVC D-Series.  I looked around for this issue but its a hard one to explain.
-Using S-Video connection

Video of problem:


It seems to me that it is some sort of resolution/refresh issue.  But I can't understand why it would work for 15-20 seconds then die.  This issue does NOT happen in windows desktop at standard resolutions of 800x600 and 1024x768.

Picture of TV boards etc:


*** UPDATE ***

I thought it was a 7800GT but it was a 7900GS.  I had an extra 7800 GT laying around so I replaced the cards and now the problem is gone.