Yesterday Apple rolled out Thunderbolt Software Update 1.2, adding support for the company's new Thunderbolt Gigabit Adapter, but it appears that the transition has not been smooth for some. A number of users have reported boot problems through Apple Support, ranging from kernel panics, installation errors, restart messages, and getting stuck at the boot screen — each of which have resulted in a non-functional Mac.
We don't know exactly how widespread the issue is, but it isn't affecting everyone, including members of The Verge team. Reinstalling Lion appears to be a solution to the problem, at least until Apple delivers an official fix. If it isn't absolutely necessary to use the Thunderbolt Gigabit Adapter at this moment, it would probably be wise to stay away from the update for the time being.