I copy-pasted the wrong thing from my notes, sorry.
I know that I resolved it by changing that reg entry but I think it may have side effects of no metro apps.
Worst case scenario would be to make .reg files, one Enable, the other Disable and double click on them when needed, but I hope someone else will come along to suggest the real ownership solution to this.
One word of caution, I would image your OS partition before doing major ownership changes on the system, because of potential side-effects. It's one thing if you do one or two reg changes but any operations affecting the entire C: drive, I would image to be safe in case major changes have major side effects.
When I played around with that trying to resolve a similar issue, I had to reimage back after major changes to all files on C: drive ownership messed things up for me when I did it.