Herman, thanks for your comments, very helpful. I ran mt-daapd with a music directory of just 17 songs, and it ran successfully for 7 hours withour crashing, so may be some combination of the large number of songs (=long rescan times) and the Maxtor drive spinning down.
I’ve now turned off the autoscan and will let it run until tomorrow morning to see what happens.
I guess I don’t really need the auto scan, I don’t add songs that often so I can just do a rescan via the web interface.
/P-O