To enable error reporting...
- press "Escape" to open the WoW menu
- click "Interface"
- click "Help"
- make sure "Display Lua Errors" is checked
- clock "Okay"
- click "Return to Game"
- type '/nui rl' and press Enter
See if any errors get reported when it reloads. If they do, just take a screen shot and post it here using the paperclip icon in the message editor or by scrolling down the message editor page to the "Manage Attachments" button.
Thanks