Today a guildie and I both noticed that any time we entered a loading screen, some unselected talents that we had put on our bars would disappear. (For example, on my druid I put both Force of Nature and Renewal on my bars. When swapping talents to others in that row, when I hearthstone my Renewal disappears off the bar but Force of Nature remains.)
There are other complaints of this happening too (Certain talents keep disappearing from my action bars - #3 by Aamarok-area-52, Are anyone's talents disappearing from their bars?), and it would be great to get this bug fixed because it is incredibly frustrating to have to keep adjusting talents on the fly!