Can't remove a folder share permission

For some reason, I have all folders in my "Documents" tree shared with
another (non-admin) user on the PC. I dont want this user to have access to
my files in this folder or its subdirectories

So, I select properties/sharing and select "stop sharing". After several
minutes (!!) it returns "You could not stop sharing the selected folder" and
the reason given is "This folder is in a shared folder".

I don't understand what this means exactly. The Documents folder is directly
uder the Users folder and this does not appear to be shared to other users
on the PC, although it is available in Network places on other PCs on the
home network. Other (non-admin) users on the PC do not have this unwanted
share, only the one user in question.

I am an "Admin" user. Vista Home Premium. How do I get this shared access to
go away?

TIA James :-)

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James:-)