This:
https://rejzor.wordpress.com/2015/06/28/net-framework-3-5-error-0x80071a90-during-installaton/
I still keep on getting reports from users. And it has been more than a year since I posted that. I’m pretty sure I’ve mentioned the bug here. Makes you wonder, what else does avast! block like this and people never managed to pinpoint it back to avast! ?