Yup, what you got was the CD laser packing up. In each optics unit there are two laser diodes, using common lenses, one for CD's (780 nm), and one for DVD's (650 nm). If one or the other fails then you get the inability to read one type of disc or the other. Cleaning the lens is unlikely to help, as the same lens is used for both lasers, though it never hurts to try.