How to solve Mcx1-user issue

If you have any problem with your current MCE-to-XBOX360 configuration and
you have to set up a new connection (with new XBOX password), you may end up
with the following issue:

old Mcx1-user will not be removed from your MUSIC-PIX-VIDEO shared folders,
and an unknown user will display in the access list.

To solve the problem simply manually delete this user from the those
folder's security list.