Microsoft fixes Cortana bug, breaks Search and Start Menus

Microsoft has confirmed it is currently investigating a second issue with its Windows 10 search service, apparently brought about by a hotfix released to patch a previous CPU-guzzling issue in the same service.

Reports of an issue with the Windows 10 search subsystem, which is integrated into the company's Cortana virtual assistant platform, began to surface following a security roll-up released late last month. Once installed, the patch caused the SearchUI.exe process on selected systems to begin to constantly drain CPU resources - pulling up to 30-40 percent of a system's total CPU time, even when not actively searching. Embarrassingly for Microsoft, and by no means alone, the fault had previously been reported through the Windows Insiders beta-testing programme - but, as with a serious data-loss bug in the October 2018 update, was ignored and the patch released to the public regardless.

The good news for those affected by the update was Microsoft discovered the problem and issued a fix, released earlier this week as part of the company's regular Patch Tuesday update cycle. The bad news: The cure appears to be worse than the disease, with users now complaining that search is entirely broken as a result of the patch.

Following the installation of KB4515384, users have reported that both the search subsystem and the Start Menu itself are failing to operate correctly - displaying frequent errors including a helpful warning that 'your Start Menu isn't working.'

Oddly, Microsoft's support page for the update claims there are no known issues, which is contradicted in a separate document on the company's site. 'Microsoft has received reports that some users are having issues related to the Start menu [sic] and Windows Desktop Search,' the company confirms. 'We are presently investigating and will provide an update when more information is available.'

In the meantime, Microsoft is pointing those affected to its guide to troubleshooting Windows Search issues - though without any guarantee that they will fix the issue. The alternative, of course, is to uninstall KB4515384 - though this will leave users at risk of attack from a range of security holes the patch was designed to close.