Microsoft has advised users to uninstall a recent Windows 11 security update after widespread reports of system instability and application failures.
The January 2026 update, identified as KB5074109, began rolling out automatically on January 13. Soon after, users reported serious issues, including frozen screens, application crashes, and display failures.
Many complaints focus on Outlook Classic, particularly among users who rely on POP email accounts or local PST files. The problems appear more severe when those files are stored in cloud-synced folders such as OneDrive.
Affected users say Outlook becomes unresponsive, refuses to close, or repeatedly re-downloads messages. In some cases, the app becomes unusable.
⚠️ Windows 11 KB5074109 Update Breaks Systems
Source: https://t.co/gFHigG7sbS
Microsoft's January 2026 Windows 11 security update KB5074109 has triggered multiple system stability issues, including lockups and black screens, prompting users to uninstall it.
Reports highlight… pic.twitter.com/LVmzGwLfc1
— Cyber Security News (@The_Cyber_News) January 23, 2026Microsoft has recommended switching to Outlook webmail as a temporary workaround. The company has also advised users to uninstall the update until engineers release a permanent fix.
Problems linked to the update extend beyond email. Users have reported black screens during startup, reset desktop layouts, broken File Explorer customisations, and apps freezing when accessing cloud services such as Dropbox.
Microsoft has published a support document outlining interim solutions. These include moving PST files out of cloud-synced folders and relying on web-based email. However, the company warned that uninstalling the update may leave systems exposed to security risks.
Engineers are actively investigating the root cause. Microsoft said it plans to deliver a comprehensive fix through a future Windows update.
