Well that narrows it down a little, but still no signal when I flip the HD switch on the cable. The jacks are color-coded, but they don't match the cables. Here are all the jacks on the back of my TV going from left to right:
PC - Audio In - Y Pb Pr - DVI Audio In - HDMI - Optical - YPbPr Audio In - Headphone out - SVideo - CVBS (yellow) - L (white) & R (red) SVideo/CVBS Audio In
- R (red) L (white) V (yellow) AV OUT - RF Input
My cable box is connected to the first "Y Pb Pr" section, the "YPBPR Audio In" section and RF Input. The red & white audio X-Box cables are connected to the l & R SVideo/CVBS Audio In" section. So I figured the blue, green and red video X-box cables would have to go in the three AV OUT jacks, but I've tried all sorts of combinations and nothing seems to work. There's just nowhere else to plug them in.