I suggest to clean a lens with isopropyl alcohol (IPA) first. In majority of cases proper lens cleaning solves the problem.Try this, but if it's still no good, it's new laser time CDM12.5 / VAM1205
cheap enough, and if your just a little mechanical an easy replacement Go the whole mechanism as it's easier than just replacing the laser.
http://www.ebay.com/itm/For-Philips-OPTICAL-PICK-UP-Laser-Driver-CDM12-4-12-5-VAM1204-VAM1205-Mechanism-/152357329357?hash=item23793459cd:g:pFAAAOSw3mpXGye-
Cheers George