FWIW, I upgraded my laptop yesterday from W7 to W10 Home.
And while I was at it, decided to update Avast to the latest (.2276) version as well.
Usually, I'm very cautious about upgrading AV packages, because of the risks and the tremendous waste of time when something goes wrong, but by the time I checked the forums there were no signs of trouble yet.
I was simply too quick.
At the time of this writing, there is a sticky at the top of this thread saying that they are aware of the problem and are working on it...
Edit: extra post.
UPDATE:
The problem lies in the communication between the GUI and the Avast services.
This means that despite the error message you see in Avast, the services/shields/protection are active and running.
A fix should be released soon..