I bought a Koss KS5190 about 5 months ago and it has worked perfect until a couple of days ago. I had bought a bunch of new DVDs and most of them work, but the Elektra DVD doesn't work in it. I put the DVD in the system, the system spins it for about 10 seconds and then says there is no DVD inserted. The DVD works in my other DVD players that I have. Any ideas why it won't play that DVD?