Denon CD unit will not play due to err

It shouldn't play any CDs as it is a minidisk recorder.
Try to stay on topic.

is this happening with all the cds??
the case may be with the cd sometime..where the tracks wouldnt have been properly completed...

Optical pick up of your unit requires replacement.

This was addressed in http://www.fixya.com/support/t557928-denon_udcm_m7_cd_player_often_reads_err

Simply remove the outer casing and remove the jammed disc

Then the format can't be read by the MAC, what reason this is I have no idea.

Oh, i had this problem several times... look, the best answer that i can give you is to buy a new one, there's sony's cd-players that are great, me and my father have. now, if you want to stay with this cd player just insert the cd several times until it will play. but again, you better buy a different one.

Try cleaning the laser first. Take care, because it is delicate.

Some instructions of how to clean a CD laser:
http://www.wikihow.com/Clean-a-CD-Player

If the cleaning does not fix the fault, it is possible that the laser is weak, or there are some problems in the electronics in the CD player. This is not something you will be able to service yourself, unless you are properly trained, have experience, and have the proper setup to perform CD player servicing.

In most cases these CD players are not cost effective to service. You can contact the orignal manufacture for details or any recomendations.

Jerry G.

You seem confident enought to take it apart, have you tried cleaning the runners that the laser runs backward and forward on.
Some times they collect dirt/dust and the laser can't move smoothly so it jerks and skips.

you could try this http://www.fixya.com/support/t244156-denon_2910_cd_player_malfunctions or clean the lens