Avast may be causing this Help!

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Can't uninstall avast antivirus, even with the utility, it just won't open, no application will open. it wont let me uninstall avast or close it from the task manager. I recently reset my pc everything was fine up intill i installed avast. help.

error when opening application: the application was unable to start correctly (0xc0000005)

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I've recently encountered the same issue.  Currently I'm on the Insider Preview copy of Windows 10 Pro.  Specifically, an evaluation copy of Build 17677.rs. Prelease.180520-0940.  I've tried 4 different times to add the update for Windows Definition Antivirus - KB2267602 on May 26 (Definitions 1.269.143.0, 1.269.145.0, 1.269.148.0 and 1.269.149.0), but each time, attempts at launching Avast result in an error of 0xc0000005 in Avast UI.  My system is also unable to launch any desktop media players, email programs, Word, and various other issues.  Uninstallation and reinstallation of all problem apps also becomes impossible outside of Safe mode.  But as soon as I go to Safe mode, uninstall Avast, and restart normally, everything works.  That is, until I reinstall Avast, and all problems return.

[bob3160]

Avast is not designed to run on Windows 10 Preview Builds.