Argh!! What a *nightmare*. After the mass of Seagate 7200.11 failures worldwide and many heated complaints directed at the company for it, despite Seagate having responded by releasing a supposed firmware fix and free data recovery processes (should it be required), apparently many users are reporting this firmware 'fix' is actually KILLING drives that were previously still working fine; this directly after a successful update.
Some users have reported in Seagate's forums that they were able to flash back to the original (offending) AD14 firmware and regain access to all their data, but others haven't been so fortunate! - Looks like Seagate will be busy with their free data recovery service.
More info here.