You may have stumbled upon this MS Article (specifically the CAUSE section).
Your trouble is most likely the fact that "my documents" folder is a special folder and to get permission to do anything in this folder requires an act of god.
Alternatively, have you tried with linux live cd? Good Luck
edit: try remove from share/homegroup. sorry, that's all I can come up with.
I, also, excluded it from the HomeGroup and the Sharing, but it still remains.