Any ideas why my Denon 3910 is very problematic at times playing some DVD disks. I have 3 players, 2 which are much cheaper and every DV plays on them, yet the 3910 just doesnt like loading some or just wont play them at all!!!! Always the other two players will! The Denon is very touchy! why? Does it need some download or something to make it more tougher???