Sony firmware update 1.0.05.12140 released today for European PRS-T2 disables jailbreak functionality (ability to boot from SD cards) on the "virgin" PRS-T2 units. I would recommend that no one installs this update without first installing the jailbreak. If the jailbreak was installed prior to "upgrade" to 1.0.05.12140, this package
should recover ability to boot from SD. It can be installed in the "usual" manner (no SD card required, unpack on a PC, run "flash_reader.bat").
The units with 1.0.05.12140 installed over non-jailbreaked firmware, or pre-installed at the factory, are not hackable at present time.