The input from your DVD is (i'm guessing) a digital signal. All your "analog" inputs will still work. If you have the audio input on your Onkyo set to "auto coax1", then you need to be sure your DVD is connected by a coaxial audio cable to the "coax1" input on your Onkyo surround system. If the cable is not an RCA coax cable (thicker cable with metal at either end), but rather an optical cable (little lenses at either end), you will need to change the digital audio input on your onkyo to "optical 1 auto" and make sure the cable is plugged into both your dvd and surround. Also, if you are using an optical cable, make sure there are no "kinks" or small loops in the cord. This would cause the signal to be completely cut.
Also, you might need to check your DVD player setup and make sure that the digital output is enabled.
Best of luck and feel free to email me if u need more help.
sewellp@yahoo.com
Patrick Sewell, January 2008