Microsoft Probes Windows 11 Boot Failures After January Updates
Microsoft is actively investigating a critical issue affecting some Windows 11 devices that fail to boot properly after the January 2026 updates. Users are encountering the “UNMOUNTABLE_BOOT_VOLUME” error following the installation of the January security updates, specifically the KB5074109 cumulative update.
Overview of the Boot Issue
The problem primarily impacts Windows 11 version 25H2 and all editions of version 24H2. Affected devices display a stop error during the startup process, presenting users with a black screen featuring the message: “Your device ran into a problem and needs a restart.”
Details of the Reports
- The issue was first noted after the updates released on January 13, 2026.
- Only physical devices have been reported as affected; no issues have been identified with virtual machines.
- Users must perform manual recovery efforts to restore functionality to their devices.
Microsoft’s Response
In response to the growing number of reports, Microsoft encourages affected users to provide feedback through the Feedback Hub app. The company is investigating whether this boot issue is related to recent updates.
Future Updates and Fixes
Microsoft has stated that it will confirm if the boot failures represent a regression caused by the January update. They have committed to updating their documentation as more information becomes available.
Additional Recent Updates
In conjunction with addressing the boot failure issue, Microsoft released emergency out-of-band (OOB) updates on the same day. These updates aim to resolve a freezing issue in Microsoft Outlook, which has been problematic when PST files are stored in cloud services like OneDrive and Dropbox. The freezing issue particularly affects enterprise environments where Outlook is commonly used.
For users experiencing these problems, staying informed through official Microsoft channels will be crucial as the company works on solutions. It is essential to ensure that any updates received are monitored for further developments regarding the boot failure issue and Outlook functionality.
