[ubuntu] administrator user has restricted access to files

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http://ubuntuforums.org – Using Ubuntu 12.04 LTS I constantly have problems with restricted access to certain files and folders. I am logged in with a user account listed as "administrator" but I am not able to copy anything from the home folder to, lets say /usr/share/apps in order to do that I need to start gnome commander as "administrator". Is this problem by design or do I have to change something in my user account? (Hardware)