If you're absolutely sure the lens is now clean, I'm not sure what else you can do. Cd players aren't really serviceable to most people.
It could be a number of things. Faulty capacitors, collapsing lense or failing spindle..even dirt around the motor or cogs can throw it off. These are the more typical failings in a drive. The DAC, board or wire damage etc.
Which unit have you got? The normal stereo or one of the more fancy things?