Brushes The Stamp problem in Photoshop CS6

#2
You need to select a different source location with the ALT key, if you have already done that you could try resetting Photoshop preferences

To restore preferences quickly using a keyboard shortcut: Press and hold Alt+Control+Shift (Windows) or Option+Command+Shift (Mac OS) as you start Photoshop. You are prompted to delete the current settings.