I have a spare set of component video cables. Is there any reason that I couldn't take one of the interconnects that are sold for component video hookup and use it as a digital audio coax interconnect? Is there something different about the bandwidth or impedance of the component video cables that would interfere with transmission of a digital coax signal?

No, there is no problem.

I do it myself actually from my computer..

You could use any rca cable. It'll work fine :)

What he said, almost.

Component video and digital audio cable are both supposed to be 75 Ohm coax (although the RCA phono plugs themselves are not). So video cable can be used for digital audio.

However not all RCA plug terminated analog audio cable is 75 Ohm coax (there is no required impedance for audio), so you can't correctly say that all RCA coax cables are interchangeable. That said you may find in pinch that almost any audio or video cable will work for analog audio, digital audio and video.

What trekguy said. Video and digital audio over coax require a 75ohm cable, thus are interchageable. Audio does not, therefore may well not be 75ohm, and is inappropriate to use for those tasks, although the reverse is just fine.

A non-75ohm coax may still work okay, but because of reflections in the wire you may experience dropout with digital audio, or will likely get ghosting with video. Nothing will break though. Still, given that 75ohm coax is absurly cheap, there is no reason not to use the proper cable.