Microsoft this week issued its first Patch Tuesday cumulative update for PCs on the recently released Windows 10 April 2018 Update (version 1803). But while the update fixes several bugs present in the initial public release, it appears to be causing some issues of its own (via Windows Latest).
A number of users have reported that installing the Patch Tuesday update is causing their computers to be unable to boot. The problem doesn't affect everyone, and it's unclear how widespread it is or if there is a common theme among those affected. However, a large number of users on Microsoft's Answers forum say they've hit the same issue while trying to install the update.
At the time of this writing, Microsoft hasn't responded to the growing thread of reports.
This isn't the first problem to crop up with the April 2018 Update since its release. Earlier this month, Microsoft acknowledged an issue causing PCs to freeze when using Chrome and other apps. A fix for the problem was expected as early as this week's Patch Tuesday update, but it ultimately wasn't included in the release notes (Microsoft has updated its release notes, noting that the fix was included).
If you do find that your computer is unable to boot after installing update KB4103721, the recommended fix is to roll back to a previous build. We'll update this post with more information if Microsoft provides an official workaround.
