Dirty laser? I cleaned one in my MacMini few times using cleaning CD, but recently it refused to recognize CDs even after cleaning. I open the case and cleaned leaser gently using cotton Q-tip and Isopropyl alcohol. After that everything works fine again.
Some people reported improvement with a little bit of silicon grease on the gears/rails but it might not be solution for you.
Some people reported improvement with a little bit of silicon grease on the gears/rails but it might not be solution for you.