Apple’s Thunderbolt Software Update 1.2, which adds support for the company’s new Thunderbolt Gigabit Adapter, is reportedly turning some machines into big shiny bricks. One PSA on Reddit urges folks not to update, citing evidence in Apple’s support community where hundreds of affected users are reporting boot-related problems such as kernel panics, getting stuck at the gray boot screen, unexpected error message and more according to TidBITS.
Regardless of the details, in each case it seems that the Mac is rendered unusable, even thunderstruck. I’ve now heard from some people for whom the update did not cause any problems, but it’s still unclear what the difference may be between those who are and are not suffering boot failures.
I hope users experiencing this issue use Time Machine, because (as of now) the only way to fix it seems to be by reinstalling OS X Lion. If you haven’t updated yet, you’ll definitely want to hold off until Apple addresses a fix.