OK, I've installed Rune Audio, found all my audio files on my NAS and it appears to play them.
I had assumed that for test purposes, I could simply plug headphones into the RPi audio jack but I'm getting no output. Have I made a wrong assumption? I believe I have configured the sound path correctly under MENU but I'm open to suggestions in that area.
I just tried another Raspberry Pi and it works OK on that one. Both are Model-B's - the one that works has 256 MB ram, the one that doesn't has 512 MB.
I don't suppose that extra memory would prevent the analog audio from working so it looks like there might be a hardware problem with that one. Bummer, I just bought that one a few weeks ago and hardly used it.