A few Windows 11 users have been affected by a bug from the latest Windows 11 security update, which resulted in their PCs refusing to turn on. According to an AskWoody forum post, there were reports that some devices encountered an “UNMOUNTABLE_BOOT_VOLUME” error after installing the January 2026 Windows security update. The affected computers came up with a black screen and a message that says “Your device ran into a problem and needs a restart. You can restart.”\
This isn’t the first issue that came out of Microsoft’s latest Windows security update, with some PCs refusing to shut down or hibernate, and another bug resulting in Cloud-based apps, like Outlook, OneDrive, and Dropbox, not working, as reported by Windows Central. The company has since released emergency updates to address these problems, but it seems that there is no fix for the unbootable error just yet. This is also the most catastrophic error yet, and the only workaround for this is to enter the Windows Recovery Environment and uninstall the latest security patch.
These security updates are supposed to keep Windows users secure, but it seems that they’re causing more harm than good at the moment. This also isn’t the first time that an update wreaked havoc on the popular operating system, with the August 2025 security update breaking recovery tools on both Windows 10 and 11. Another security update in October brought another issue, with USB keyboards and mice not working in Windows Recovery Environment, meaning users cannot actually do anything to troubleshoot their PC.
It’s unclear what caused the latest issue, and we’re still waiting on Microsoft to release an emergency update that will fix the problem. However, this is probably easier said than done, especially given that millions of PCs with a nearly infinite number of different hardware configurations out there have Windows 11 installed. But even if only a small number of Windows 11 users are affected by this catastrophic error, it’s still an issue that needs to be addressed quickly.
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