Yesterday, we fixed up a couple of the machines by doing a system restore and delaying all updates because we were not sure of the cause. I'm now seeing postings that indicating that removing the font cache file may allow the system to boot. Delete this file:
I should note that I don't think this is widespread as we've only had one client with the issue. Strangely it was their Engineering users with the issue. So, I'm guessing it's some type of software interaction causing the issue.
If you are using WSUS, I strongly suggest you decline KB2982791.
Update: Further reading suggests that KB2970228 is also bad and should be declined at this time.
Update, Aug 29/14: More drama. Apparently the replacement update for this also has some issues. Although less severe. Read someone else's rant here: