If you see a padlock next to a content item in the administration panel of Joomla you can remove it if you have adequate Admin access rights by going to the toolbar / menu item System and selecting Global Checkin from the drop down menu.
The padlock is a symbol that represents that some one else is editing the page you wish to edit... which is why Joomla! won't let you edit the page.
However sometimes it doesn't properly unlock a file hence the need to do global check in.
