OK... I swapped the cables. Both DVD players passed a 720p signal through the DVI connectors. I swapped them back and both still passed a signal. The big difference this time... I only had one DVD player on and outputting a 720p signal at one time.

So, it would seem having both DVD players on and sending a 720p signal at the same time confuses the DVI switch. Looks like the 970 will play the first 720p signal that hits the switch.

Cheers,

PeteH