OT: medyo misleading yata yung thread title...
Cinavia is now part of AACS, which is the DRM used on Blu-Ray discs. Based on what I remember, it's implementation would be compulsary for all licensed playback devices starting Feb 2012. As you describe it in your experience, I see that the Cinavia feature is working as intended (i.e. disabling HD audio track on protected movies when played from unauthorized copies)
As long as everything is "legit" on your end, then there shouldn't be a problem. And in case you encounter difficulty playing genuine BDs with the latest firmware, that's the time you report issues with the firmware.
IMO, the more appropriate title should be something like "Sony BDP-S480 - How to downgrade firmware" or "How to circumvent Cinavia" or something to that effect...
As to your current predicament of not being able to play "unregistered blu ray movies (in short pirated copies)," for that purpose i would suggest getting an NMT or a secondary non-compliant BD player (i.e. older player which has not yet been updated)