For some reason it is not reading the TOC (Table of Contents) correctly. If it cannot read the TOC it considers the disc to be single sided. Disc could be slipping in the clamp and the TOC could not be read in the specified time allowed.
Try putting the disc in the tray and then press "Side B" to close the tray. See if it goes to side B.
Also; do you have the problem with ALL LD's you own?