I'd look at the keybinding. Especially if you're using a bar mod (my experience is with Macaroon but it's probably generally applicable), make sure that key is explicitly unbound before binding it. I mean, don't just re-bind it, but go to the standard WoW keybinding interface and un-bind it by clicking on an empty space, binding it to your key, then click it again and hit the Unbind button. Now it's definitely un-bound and you can re-bind it, whether through WoW or your bar mod. I don't follow this for every keybinding I make, but it often fixes problems after I detect them.