Encspot and Mp3Trim find no errors with the files that are failing and no software has any problem playing them.

Good diagnostic step. Thanks for checking that first before posting.

I do get the occasional “Hard disk not found” error, but it hasn’t happened in a while and every time it has, rebooting the player has taken care of it.

That would tend to indicate a hardware problem that needs to be solved, and could easily be the reason you're getting the errors.

but the same tracks will fail every time.

I'm not certain I buy that. Can you elaborate and be very specific of what/how you're uploading to reliably reproduce the specific-track error on multiple separate occasions?

Some things you didn't mention:

- What version of the player software are you running, and what version of Emplode are you running?

- Are you doing it with USB or Ethernet?

- What operating system are you running?

If the answer to those last two questions are "USB" and "XP", have you looked here?