Hello Jim,
I recently encountered problems with an SX20 and a C20 where the digital audio from our PC, connected to input 2 (the DVI connector with a passive HDMI adapter) "was" passing digital audio from the PC to the codec but stopped about a month ago.
No changes to the codec, no firmware updates performed no reason for anything to change.
The Windows PCs and laptops that we use are standard but now Windows no longer detects an "audio display device" on the SX20 and C20 DVI inputs, this was not the case when the equipment was installed.
Is this the problem you are describing or is it the audio output?