Found this article by Rick Burgess today on Techspot for anyone who is using Thunderbolt Drives!!

"A growing number of Mac users are reporting a critically serious "kernel panic" error with some Macbooks and iMacs."

"Although Apple hasn't officially acknowledged the issue yet, all Mac users are urged to avoid the Thunderbolt update until a fix is issued. Once a Mac is hit with the bug, it is basically rendered unbootable until the problem is fixed or Mac OS is reinstalled. For temporary access, I suspect safe boot still works though -- hold the shift key during boot."