DvD TSSTcorp CD/DVDw SH-S182D glitchess+and crackles

when i put DVD or a music cd into my (TSSTcorp CD/DVDw SH-S182D)
i get slight problem, for e.g if its a dvd the picture glitchess,and the audio crackles as if my stereo aux was damaged. ive opend the cd dvd driver case and had a look and no sign off dust or and dirt!.
ive also checked my tests on dxdiag ere a log file there nothing else i can think of atm its winding me up please help if you can

btw when i play my music dvd files off the pc directory its fine, onlywhen i insert cd's thats when it starts to glitch and crackle