Windows Defender on Windows 8.1: Real-time protection couldn't be turned on

[Guest iad58]

This seems to be a common question, but I can't find an answer that would work for me.

 

 

Am running Windows 8.1 on a new computer. (I bought it with pre-installed Windows 8 and upgraded it to 8.1 before doing anything else with it.) As of several days ago, Windows Defender (which is otherwise up and running) states: "Real-time protection is turned off. You should turn it on". When I click on "Turn on", after a few moments I get the answer "Real-time protection couldn't be turned on. This operation returned because the timeout period expired." The error code is 0x800705b4.

 

 

I used to have a McAfee antivirus installed, but uninstalled it (using its own tool) and manually deleted all mention of it in the registry that had been missed.

 

 

Scanned the computer, no malware is reported.

 

 

Rebooting doesn't solve the problem (as I see it does for some other people).

 

 

Help?

 

 

<Moved from security privacy/win8.1>

 

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