I also got exactly the same problem after upgrading to the latest firmware.
I never set any password to the card, I never used remote lock feature and the card was reading just fine before the upgrade both in PC and the Satio.
I contacted Sonyericsson they told me they never heard about this problem, but apparently alot of users seem to experience the same thing.
The answer was: Buy a new card.
I will never give up in pushing SE to solve this, because of the great camera I have ALOT of family photos on the card which I no longer can access.
Meanwhile I am using another SD card because I will never format the card, then the data will definitely be gone.
EVERYONE who has the same problem, POST EVERYWHERE about it, because if we dont, then SE will not solve this problem for us! I even contacted Nokia about it, still no response.
Fred, April 2010