this is what I found.

"You are going to have to take your DVD drive apart. When you do take it all the way down until you see the laser again,(we are starting all over just like when you cleaned the laser). Now look at the rollers, if they are open that means it thinks there is still a disc inside. While it is apart (please be very careful) plug your PS3 back in and hit the eject button, make sure that the rollers go forward and the laser and caddy go down. Next just place the top on your DVD drive and try to insert a disc, make sure the magnet is on top too. It should take the disc at this point.If it dosen't then keep hitting the eject and try to insert a disc again.. when you hit the eject with no disc in it, and it beeps twice then you know its reset and ready for a disc.Then go ahead and put your PS3 back together. What happened is your PS3 thinks that there is still a disc inside of it and won't let you insert another, until you reset the rollers and "dogs" it won't let you eject or insert a disc. "