Well I for one enjoyed your expose. I hope it had the cathartic effect
you were looking for.

You left out some important details, like what format (ISO, Joliet) in
which the disc was burned, brand of CDR, whether the disc was finalized,
etc. But I'm pretty confident that it WASN'T the fact that you used
nested directories on your disc that caused the problem. Most major
brand mp3 decks today can handle nested directories.

Did the manual mention the burning formats that are allowed for that
unit?

Like a previous replier, I use an Alpine (CDA-7998) and it has no
problems navigating folders in the way you desire, so at least that's a
starting point. But you should indeed keep trying display models until
you find one that will play your discs. Try bringing a few different
brands burned in different ways (properly labeled of course):
finalized/not finalized, track-at-once vs. disc-at-once, ISO vs. Joliet,
etc. You could also bring a disc with all the mp3s in the root folder,
but as I said before most major brands should handle directories just
fine.

Best of luck and let us know how you do, especially if it's as
entertaining as the last one.