The most likely reason this is happening is the View All Data permission is not checked under the System Permissions for the profile of the user viewing the page.

This can be fixed by doing the following:
  1. Go to Setup -> Manage Users -> Profiles. 
  2. Click the profile of the user that you need to modify. (you can view the profile of the user by going to Setup -> Manage Users -> Users) 
  3. Under System, click System Permissions. 
  4. Click Edit. 
  5. Towards the bottom of the list, check the box for View All Data (this will also check View Setup and Configuration). 
  6. Click Save at the top.