Okay... we have a conflict somewhere then. I have no problem casting Incinerate via key bind with my Lock and your macro works fine in my bars.
Have you done a clean installation of nUI as per the instructions here:
http://www.wowinterface.com/forums/s...ad.php?t=37330
If you haven't, I would ask that you try that. Something is preventing your key binds from working correctly. I would be curious to see if the clean install fixes it or not.