Disk read error or it takes so much time, two days back disc was running smoothly but now when i insert d same disc, my player can't read it, a message appeared says disc is dirty...

My panasonic home theatre model no. Panasonic SC-HT520 is creating problem with some disk. after lots of struggle in reading it gave up, two days back one of my disc (Verbatim dual layer disc) which was copied from nero o.e.m. was working absolutely fine but now when i insert d same disc again, my player can't read it, a message appeared on T.V. says disc is dirty, but d disc was absolutely fine and it runs smoothly in other dvd players. my system is just 7 months old. and is in good condition. one more problem is that, once i copied mp3 songs on a dvd+r (hp media) from nero o.e.m., my player shows a message that 'these type of disc can not be played'. kindly suggest me some...