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.

This solved the problem for me:

1. Open the keyboard shortcuts in settings.
2. Change the 'move left and
   move right' for mission control to something new and obscure.
3. enable and change conflicting shortcuts for desktop 11,12,13 to something
   more obscure, then disable them again.
4. reset the computer.