Probably the writer is on its way out, the CD in the drive is not empty, or the chemical used for the CD is not compatible with the laser in the drive. (pretty rare these days, but it was possible in the beginning. You had drive makers giving advice on what discs to use. I remember seeing a guide someplace on which CDs worked on what drives)
if it a blank cd then try seeing if there a firmware update..some drive need them to read the newer media. if it a reg audio/dvd retail disk...then the drive may be on it way out or there some new type of dmr (anti copy code that the cd-player cant read).