Cdr's will no longer play on my laptop

Hello,

Hello,
I burn a LOT of cd's using cdr's and Itunes. last night I tried to play one through Itunes on my VAIO laptop and it's showing that I've inserted a blank disc. I've tried to play several other cdr's that I've burned over a long period of time using Itunes and they show as blank cd's as well, when they used to play on my laptop. This hasn't been a problem until last night. Now, for some reason, they won't play and every cdr I've tried shows as a blank. The cd player and Itunes, which is my default media player on my laptop plays commercial cd's just fine, but now, for some reason, any cdr I try to play through Itunes is showing as a blank cd. Any help in resolving this issue will be GREATLY appreciated. Thanks so much for your help!