Apple has released a software update for Mac OS X Lion on Wednesday night, bringing the OS up to version 10.7.4.

The 10.7.4 update is recommended for all OS X Lion users and includes general operating system fixes that improve the stability, compatibility, and security of your Mac.

Those fixes include resolving an issue where the “Reopen windows when logging back in” setting is always enabled, improving compatibility with certain British third-party USB keyboards, and addressing a problem that may prevent files from being saved to a server.

Apple has also said that the new update should improve the reliability of copying files to an SMB server. Exciting, we know.

The real reason for the update however is to fix the OS X FileVault encryption issue discovered recently.

According to security researcher David Emry, those who used FileVault before upgrading to 10.7.3 are able to find their password in a system-wide debug log file, stored in plain text outside of the encrypted area.

The update is available via the Software Update feature in OS X Lion for all users.