Today I had a SharePoint installation that started to throw errors when opening the User Profile Service Application. After examining the ULS log I noticed this log entry:

Requested registry access is not allowed.

So something with the permissions in the registry seemed to be wrong. I manually browsed through the registry settings and compared them to another, working installation but I couldn’t find anything. Luckily I stumbled across this cmdlet: Initialize-SPResourceSecurity I ran the cmdlet and everything started to work fine again.