I just had this problem come up with the latest update 3.55, none of my disks are reading anymore. I've cleaned them and checked for scratches, re-installed the system update and done a complete reinstall of the system software though the Initialize System option with a USB drive.
I've also tried swapping the Blu-Ray drive with a different one and I am getting the same error message. The system will accept the disk, then it tries to read for about 30 seconds then the drive motor makes a noise, then about 20 seconds after that I get the Unrecgonized disk message on the screen. Not really sure what I can try next to solve this.