Iyonix CD Drive not found

Sudden hiccup on my Iyonix running RO 5.16 - never happened before.

I put a music CD in the drive - it opened and closed normally, and the
green LED flashed normally. I tried to use RComp's MusicMan to play it
but it complained that it couldn't find the built-in drive. It's never
objected before, so before assuming MM had a problem I tried SmartCD+.
It too complained.

I then did a ReStart in case something else was interfering, and then
tried clicking directly on the CD :0 on the iconbar. The result was:

Message from CDFS Filer
CD-ROM drive not found

I have never ever had cause to interfere with this internal drive, (or
any other internal hardware for that matter), so have no idea what to
do do next, especially as it's LED and tray seem to me to suggest it's
ok.

Thoughts appreciated please.

--
Alex.
.