it sounds like a dirty lens - most "faulty" optical drives have only a good amount of burned in dust on the lens.
there are many ways to clean the lens - i would do it like the autor of the article - since it's the way to get it really clean
you can read about the different cleaning methoths here: [http://muzso.hu/2008/08/17/how-to-clean-the-lens-of-a-slot-loading-optical-drive-a-macbook-pros-superdrive|CLICK]
good luck