Did you upgrade to Windows 8? According to Sony Support if you've upgraded to Windows 8 from Windows 7 it will not support the BlueRay player but do check Sony Support site for any driver update for your BlueRay player that is for Windows 8 that should solve the issue. Here's other troubleshooting steps you can try.
- Go to Device Manager and uninstall the BlueRay drive.
- Reboot your laptop and it should reinstall the driver automatically.
- After the reboot test it once again and see if it would play.
- If it doesn't play try using a 3rd Party player like VLC and see if it would play normally because if it does play the problem may lie on the built in player not having the right codec to play BlueRay.