Is there a "universal" problem playing Dual Discs?

Dual Discs are slightly thicker than other discs. As a result, some players are unable to read them; the laser just doesn't line up correctly because of the extra couple millimeters.

If I were you, I'd contact the manufacturer and see if they've had success or failure playing Dual Discs in their machine.

My Esoteric DV-50 played them fine [same transport as the UDP-1 I believe], but the Denon 5910 does not play them...which might be true accross the board for the Denon players.

I believe the UDP-1 uses a Pioneer transport. Can't recall which one, though. I've sent some emails to McCormack asking, but they've not been too quick to reply.