The HomeUser (or HomeUser$) permissions group is a specific group for win7 and HomeGroup access, (the $ is often added to indicate that this group is system generated).
It is an automatically generated system group that allows any user with access to a homegroup, Read only access to certain areas of a users file structure. I'm not sure what the default access for this group is Folder wise but it is not a blanket one, but confined, I believe, to the User File links to "My documents" Etc. This could easily cause the errors you received
If you are not using homegroup then the group is not required. If you are using homegroup, I'm not sure but removing the homegroup and re-making it may well correct the application of permissions, I say "may" here as I do not have any actual proof of this, and it may be created by default on OS install and each user creation adds the user to the group.
The actual application of these permissions is also possible using the share with .... right click option in explorer on the user folders themselves.
Th best thing to do to see if you need additional permissions on this area to those you now have, is to run the system for a few days and see if you have any issues running things, especially any HomeGroup related functionality
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