This problem happened suddenly on my MacBook pro: when I insert a CD/DVD, it tries to read it for a few seconds (the motor of the DVD drive is working) and then it stops, and ejects the DVD.
I have read in many forums that this is a dead condition for DVD drive, and should be replaced. But some others also suggested the lens might require cleaning. Does anybody have experienced the second situation (i.e. can the problem be solved using DVD drive lens cleaner kits)?