depending on what ps2 you have bulky or slimline? you can either have the lens replaced or check the switches, 1 at the back and 1 at the front(on the slimline)if you are ok with opening it up there are about 7 screws under the ps2(under the rubber feet)doing this though does invalidate the warranty,and check that the switches are ok and making contact.And also check the runners that the lens runs across havent worn down and causing the lens to stop.
hope this helps
adefox, July 2007