How would an interconnect that seems intact in every way stop working, and how to fix?

Send it back to the manufacturer and they can repair it.  It's likely a solder joint that gave up.

You may have broken the wire or connection inside one of the RCA plugs when unplugging/plugging in.  Do you have access to a normal multimeter?  Most have a continunity tester setting that you can use to check the cable, center pin to center pin and outside ring to outside ring.  Most likely one or the other will not show continunity.  Also check center pin to outside ring to see if there is a short.  After that, you can call the manufacturer and see what it would cost for them to reterminate the cable.  Most will do it for a small fee.

It happens. I have had a couple of Cardas Golden Reference ICs do the same. sent them in and they repaired it at no charge. Be sure and send both cables, Cardas had changed the heat shrink from gray to black and they redid both cables

No charge except shipping.

dkidknow

As above, send those IC back to Audience. Keep me posted on the repair process.

Happy Listening!

My suggestion is make your own out of Connex pure silver interconnects so you learn how to repair your own. :)

A multimeter and soldering iron are waiting to meet you.

Thanks so much for the thoughtful replies.  I called Audience and without any hesitation or questions asked they told me to ship them both cables and they'd repair under warranty.  

That's the kind of company I want to deal with.  I'll be looking to do more business with them in the future.

Thanks again!