Today, Apple released a firmware update for 21.5-inch and 27-inch Mid 2010 iMacs.
According to the company’s support site, the update:
fixes a hard drive issue that may prevent some iMac (21.5-inch and 27-inch, Mid 2010) systems from booting properly.
Weighing in at just 767 KB, this should a be a quick one to run. It requires OS X 10.6.7 to be installed on the system.
Got a machine that this update will affect? Let us know how things go in the comments.