During April 2013 Patch Tuesday, Microsoft released an update for Windows 7 (KB2823324) which was a security update for the Windows 7 file system kernel-mode driver. Unfortunately for some users, this update has resulted in an infinite reboot loop. Microsoft had to issue another fix, KB2839011, to address the reboot bug.
Now, Microsoft is making available a new security update, KB2840149, which addresses the security issue that was supposed to have been fixed by the botched update, KB2823324. “As we previously discussed, we stopped distributing this update when we learned some customers were having issues. The new update, KB2840149, still addresses the Moderate security issue described in MS13-036, and should not cause these issues,” Microsoft stated in an official blog post.
Apparently, the original update created a conflict with certain third-party software, resulting in system errors. Microsoft had to immediately pull the update to prevent any more issues from coming up. Microsoft eventually released a secondary update which removed the first update.
If you are running Windows 7, head over to Windows Update to snag the latest security fix. If you have automatic updates enabled, you most likely have the update downloaded already!