CD-R's suddenly "unreadable".

I've been listening to CD-r's on my CEC TL-1X without any problems for the past several years. Within the past few weeks the same CD-R's have become unreadable on this transport. Ocassionally, if I start the CD on a later track, say track 10, and work my way back to track 1 with the remote, it will read and continue to play.
The manufacturer of the CD-R's are from many sources including Sony, Marantz, IBM, etc.

I checked the laser for dust and debris and all seems OK.

Any Suggestions??

Mike