My HDTV is set to alway return to a certain input when first turned on. I programmed it to start on the Component1 input, and that's where my DVD player hooks in.

It could be that your friend's TV has the same feature, and isn't on the right input for DVI until it's turned ON. He likely switches the input to watch regular TV after viewing a DVD, and might not realize it has to be back on the DVI input for his HDMI/DVI signal to work. Then it automatically returns to the DVI input when turned ON again.

Have him toggle through the inputs next time instead of turning the TV off and ON. It might find his DVD signal that way.

Dave B.