I remembered that first time it happened I had just uninstalled the avast Remote Assistance component.
I reinstalled avast (including remote assistance), and webshield was fine.
Then I uninstalled remote assistance again rebooted - and hey presto - webshield won't scan, and Thunderbird sign in pop-up is missing again!
I now have aswRdr.sys and aswRdr2.sys under C:/windows/system32/drivers. Is this right?
The former was just created after I uninstalled remote assistance.
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