Apple has issued new EFI Firmware updates for the 2011 range of Macs, which includes the MacBook Pro, the MacBook Air, the iMac and also the Mac mini. The firmware updates are available through Software Update now and weigh in at just a few megabytes. Software Update will automatically determine if your Mac is one of the models to which the update applies.
“This update improves the reliability of booting from the network, addresses an issue that can prevent HDCP authentication after a reboot and resolves an issue with boot device selection when a USB storage device is hot-plugged.”
As always with firmware updates, during the update process, your Mac will likely beep loudly, which is perfectly normal, although does give some folk a shock who weren’t expecting it.