It is not possible to go back to a previous firmware version, but it is possible to attempt to repair any bad sectors on the HDD, I tried this twice, and it still comes up with same message saying the data is corrupted.
Bloody Sony, they force you to do updates or you can't log onto the PS network, then this happens.
Massive problem in the U.S. from what I've read on the official PS forum over there.
It will play normal DVD's, and games downloaded online, just not blueray or games.

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Its just the internet dude, its not real.
F.B. Racing
01 WRX (STI badged)
2010 XR5 Focus
06 Impreza Hatch 2.0i