The disc used may be defective. The disc used may be defective, try another disc.
The disc is placed improperly in the tray. Make sure the disc is properly placed and centered in the tray and if the disc has a label on one side, make sure the label is facing up.
The disc is dirty. Use a soft cloth to clean the disc by wiping in a straight line from the center of the disc to the outside edge.
Use of DualDisc or Flip Disc which does not meet the Compact Disc Digital Audio Standard. Some music labels have recently introduced the DualDisc for pre-recorded audio and video content. The DualDisc bonds DVD content on one side 'back-to-back' with digital audio content on the other side. However, the digital audio side does not meet the technical specifications specified in the Compact Disc Digital Audio Standard. For this Reason, DualDisc is not permitted to carry the CD logo. Philips DVD and CD players and disc drives fully comply with the CD specifications and therefore may not recognize the DualDisc. Attempting to use DualDisc may lead to playback problems or jamming in the slot loader or drive. The DVD video content on the DVD side of the DualDisc should play on Philips DVD players and DVD drives. However, Philips DVD players and drives do not support DVD Audio, and will not play any DVD Audio content present on the DVD side of a DualDisc. Philips will further investigate DualDisc and update this notice accordingly.