Many times, in-game, I do something I didn't mean to (ask die, I say this all the time in my training sessions) and I could never figure out why. I think I finally got it; the accept and cancel button positions are not consistent!
If you select a toon and then decided to deselect it, you hit the deselect button (https://i943.photobucket.com/albums/ad276/Trasd/Hero%20Mages/MYDESELECTBUTTON.png), which happens to be in the same location where the accept button for a spell is positioned!
My suggestion is to ALWAYS put all accept-type buttons on one side and ALWAYS put cancel-type buttons on the other (I consider the Deselect Button a cancel-type button - maybe add some red color to cancel-type buttons and green to accept-type, too). People are creatures of habit and when we get used to something, tend to do it without much thought.
Just say'n...