Sony have released a small mandatory update which they say is designed to address security vulnerability in the system software. Although Sony have not officially stated a specific reason for the update it is likely that it is a response to the USB device called PSJailbreak, which has the ability to play cracked versions of games off the hard drive.
Since the release of this update there has been some suggestion that it is leading to a number of consoles crashing. It is not know yet if it is only affecting a small number of users, but some have also said that specific games are not working, while other gamers have reported having sound related issues.
Sony has not yet said anything on the problems some users are having, but they are only likely to comment on these issues if a significant number of users are affected.