Thanks for the reply.
I've had DSP disabled all along. I was using one third-party plugin, the iMON VFD display plugin. After the problem happend, I uninstalled it, and it made no difference.
There's nothing particularly unusual about my setup, but I did notice that at least 3 of the times the error has occurred, it was when the player was switching from a mono to a stereo file. My mono files are true mono files, which may be a bit unusual. I use flac format.
One other thing that I happened to think of was that I made one hardware change just before this started. I finally got a network cable run into this room, so I removed the wireless card I had been using, and enabled the bulit-in wired adapter. I can't see how that would make any difference, but I went ahead and disabled "Media network" in MC17 (I wasn't using it anyway). The error hasn't happened since, maybe I've found something. If it goes a few more days. I might re-enable the option and see if it comes back.