I think I might have found a bug. I am using nUI+ version 5.06.12. I was on my hunter in Northrend when I encountered a possible. In Zul'Drak there is a quest chain that ends with the final quest that is Betrayal. Through out the chain you have to use an item to gain control of certain things within the game while being disguised. They end up becoming a pet with an action bar. When this occurred I couldn't use the pet bar. I actually had to log out and disable nUI in order to complete the quests. When my normal pet was active it worked fine. The problem only happened when I used the item to gain control of a mob.