On June 11 Apple announced a couple of Thunderbolt adapters to provide Ethernet and FireWire connectivity to Thunderbolt-based systems, and issued a driver update for OS X to provide software support for these adapters; however, for a number of users the update resulted in the inability to boot. Apple has reissued a fixed version of this update, which should install properly without any issues.
The driver update is a small plug-in for a required system kernel extension to give it support for the new adapters, but when installed prevented the system from loading the driver properly, which caused some systems to start up to an international "no" symbol, and caused others to kernel panic during boot with a message similar to the following:
panic(cpu 0 caller 0xffffff800064ba7b): "Unable to find driver for this platform: \"ACPI'.\n"@/SourceCache/xnu/xnu-1699.26.8/iokit/Kernel/IOPlatformExpert.cpp:15 04
Attempts to start up in safe mode and otherwise clear the problem did not show any success, leaving reinstalling, restoring from backup, or reapplying the combo update via another Mac the only options for fixing the problem. Apple acknowledged the problem and subsequently pulled the update from its software update service, but has now rereleased a fixed version of the driver that should work properly. As with the prior version, this latest update is available through Software Update, but can also be downloaded from the update's Web page.
Since the initial release of this update has proven the potential for problems from software updates, even though Apple has fixed the update, be sure to fully back up your system before applying this new update or any others.