Apple just released new firmware updates for the full range of Macs released in 2011, which apparently all fix the same issues.
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.
The software updates are:
– Mac mini EFI Firmware Update 1.6 – Mac mini (Mid 2011)
– iMac EFI Firmware Update 1.9 – iMac (Early 2011)
– MacBook Air EFI Firmware Update 2.4 – MacBook Air (Mid 2011)
– MacBook Pro EFI Firmware Update 2.7 – MacBook Pro (Early 2011) and (Late 2011)