I go into the Application manager, click "Check for Updates". In the list that is returned is "Operating System". I select that and hit "update" then I get a message "Unable to install. Software contains updates to packages installed from a different source and is likely to harm the system. Contact software author. Continue installing?"

Matter of fact, the above message is displayed for all of the items in the Check for Updates list: map, makedev, libglade2-0. Should I hit that "Continue installing?" button?