Instructions
Ensure that your PS3 is plugged in and powered off.
Hold down the "Power" button for approximately 10 seconds.
Wait for the power light to turn red and then let go of the "Power" button. This indicates that the hardware settings for the console's internal components, including the Blu-ray player, have been reset.
Unplug your PS3 console from the wall and then plug it back in and attempt to use the Blu-ray player in your PS3 again.