Yeah tell us how it is wired up. According to the manual you have to set all the inputs to HDMI1 for both audio and video. However the buttons on the 975 remote appear to be hard coded to the inputs of the HDS42.

For example if you hit the DISC button on the remote the DISC input on the 975 has to be set to HDMI1 for both audio and video. However the DISC button selects the HMDI2 input, and ONLY HDMI2 input, on the HDS42. It will not detect automatically.