The PS3 had some lens problems when the CECHG came out, when a lot of the lens wouldn't read discs (like your problem). If it is still under warranty, you can send it to Sony to fix for free, or you can opt to change the lens mount. What you need to do is to open up the PS3 and change the lens, or lens with mount. The mount (or deck) is the part that also includes the lens motors. If you search on
http://www.edepot.com/playstation3.html on "lens" you will see that different lens model numbers were included for different PS3 models. Your lens model number should be KEM-400AAA (with mount). KES = without mount. KEM = with mount. But to be sure, you should open it up to see. Then search on internet for people who sell your part, and change it yourself.
This is what the part should look like:
http://images.google.com/images?q=KEM-400AAAWithout lens mount:
http://images.google.com/images?q=KES-400AAAI'd recommend you get it with the mount so you don't confuse which lens goes with what mount.
Models CECHH and later use a different type of lens (two lens instead of only one):
http://images.google.com/images?q=KES-410ACAhttp://images.google.com/images?q=KEM-410ACABut again, to be sure, you should open up you PS3 and check if you are going to order. If it has two lens, go for the later model, if it has one lens, go for the earlier model. If you have the CECHE, take some pictures of the motherboard as well.
viewtopic.php?f=9&t=1376 and post a followup there.
Another quick fix is to simply make sure you don't put dirty Blu-ray discs inside your PS3, as it might end up getting cleaned by the lens! Thus making your lens dirty. If it is just dirty lens, you can try to blow the particle off of it, or use those eyeglasses cloths to clean it. Don't use regular cloths or tissue as it will definitely scratch the lens! It is best you not touch it, as that lens is extremely delicate, so unless you have special cloths you can try wiping it clean and see if it works.