Sudden Shut Down for Some Sony Xperia Z Owners
Despite being waterproof, scratch-proof and dust-proof, the new Sony Xperia Z isn't completely proofed from every threat as some owners are finding out. These owners are reporting that their Sony Xperia Z smartphones are shutting down for no reason and then not turning back on again. Some have reported success at bringing them back online by doing a hard reset (through a combination button press of the power and volume buttons) but some have not been successful. So far there have been no indications as to a common reason why something like this could have happened.
Sony has been notified and have responded that it would be solved with the next firmware update, so don't panic or throw down your new Sony Xperia Z smartphone just yet. While the problem has been acknowledged, it isn't widespread as many more Sony Xperia Z users have responded that their smartphones are fine and in working condition.
[sourced from GSMarena.com]