Can't add "Movies" folder to the Finder Sidebar

Hi there,

I have Mountain Lion on my Macbook Air. For some strange reason I can't move the "Movies" folder into my Sidebar. I've tried deleting the com.apple.finder.plist file and rebooting.

See the video here:

http://youtu.be/SoWV5Jyf9Wk

As it is far easier to show than describe.