Keyboard Shortcut for moving left/right a space doesn't work After going to:

Preferences > Keyboard > Keyboard Shortcuts > Mission Control

I am able to assign a keyboard shortcut to move left/right a space. However pressing shortcut I assigned does not activate the command. I have tried other keys which are not binded to any other system commands and they do not work as well. Other shortcut are fine 

Any ideas on how to fix this?

I am running Mac OS X Lion 10.7.1.
This helped me: 

https://discussions.apple.com/message/18340925#18340925

Paste this into Terminal (it's all one line, not two):

mv ~/Library/Preferences/com.apple.symbolichotkeys.plist ~/Desktop/com.apple.symbolichotkeys.plist

Press 'return'.
Log out and log in to your system.
Go to System Prefs and set up your hotkeys as you want.