This did the trick when Avast came up somewhat hosed this morning. The ball was spinning freely, but it had a death hold on my task bar. I could click to get the taskmgr running, but then I’d get some disk grinding and things would fade out. So after a few rounds of that, I went over to the administrator login (I could probably do this on my own power user login, but I felt it better to do as admin), did the repair, rebooted, and I’ve been good to go.
Thank you Asyn, you saved me 
I wonder if this should be made into a permanent topic at the top of the forum. I mean, I’ve seen mention of repair before, but it didn’t occur to me to try it for this problem.