Not sure why, but I was going to do some testing to see if there was increased compatibility with PSJailbreak's non-encrypted eboot.bin method found in their Backup Manager... but the games don't mount.
I freshly ripped Assassin's Creed with it... but had no luck mounting it.
Here is what I would do. First, insert a game. Then use Backup Manager to "mount" the backup of Assassin's Creed. Then at the XMB menu screen it should have replaced the title of the game that you inserted with that of Assassin's Creed. Choose to play the disc from the XMB and you should be good to go!