Avast antivirus hangs and slows down computers after Windows 8.1 update

A recent update to Windows 8.1 causes  issues with  Avast antivirus. Users complain about slow and unresponsive systems which are resolved after uninstalling Avast. The problems appear to be related to Windows 8.1 update KB3000850, after installation of the update on a system with Avast installed, the operating system becomes sluggish and applications don’t function as intended.


Users also report they are unable to shutdown their computer when KB3000850 is installed, while other users report their computer doesn’t boot into Windows anymore. By uninstalling the Avast antivirus software the problems are solved.  A reinstall doesn’t solve the issue, Windows 8.1 users report that after installing Avast again, the problems also appear again.

The antivirus vendor has confirmed the issue and states it’s working on a patch which should fix the issues with the Windows 8.1 update. The company will soon make the patch available to Avast users.


It’s not the first time Avast is in the news with issues this week, earlier we reported that Avast accidently removed FireFox extensions and yesterday Virus Bulletin announced Avast was one of two well known antivirus virus vendors that didn’t pass their tests.