Apple has released firmware updates for Intel Macs, the iMac, MacBook Pro and Mac mini.
These updates are called the SMC (System Management Control) Firmware Update. All three updates "address intermittent boot issues" with their particular model of Mac. And all three updates (which are available from Apple's support website) weigh in at under 1MB.
SMC updates are available for the iMac (early 2006), Mac mini (early 2006) and MacBook Pro (15-inch) computers.
Installation of these updates is a little more complex than standard software updates. It's a good idea to print them out before beginning the installation, Apple warns.