Yes, I had Avast running some years. For this WU failure I uninstalled it some days ago and then I mistakenly installed Avira, confusing the names. Avira found and blocked some stuff. I deleted the program and ran Windows Defender without a result and then I switched to Bitdefender free edition today. It found many unresolved threats, but just showing a few items in the "view files" list, just some threats in old backups of emails from 2005. How can I get the whole list? Just buying the full version?
I also ran CCleaner. This one proposed some programs to delete, like Windows Media Center. I did that. I also ran their registry cleaner, first time 15th of october, when the update problem ocurred. (I choose to backup before the repair and I have saved the files)