I have had this player since March of 2000 and iv had no trouble TILL i got ID-4 .
In places(not the same place)the chapter would come to a end and repeat itself.No other dvd's would do this TILL i got the new T-2 DTS yesterday. It was ID-4 all over again. I did some looking and all sighns point to the fact that thease two dvds are what the call "dvd18?"i dont know what that means but i think it another word for "DVD is PACKED full of stuff."If you have any trouble with thease two dvds doing this same thing,let me know.By the way... my dealer is giving me a NEW player of my choice,im thinking of taking the NEW Denon -1000 thats hits the market in Oct.I looked at" NAD" (the stores other top dvd player they carry,)
and when i looked at the reviews over at aduioreview.com people dint have to many kind words for the T550.

just a thought, did you ever call denon and ask if they have a newer firmware that fixes it?? I had similar problems(not the same disk but weird problems with the counter and stuff when a dvd would hit a certin chapter) with my pioneer DV-525 and i called them and they upgraded my firmware to the newest one and it fixed everything. Mabey befor returning it you should see if denon has a new firmware.