Generally if you right-click while casting a spell you can exit casting. That didn't work?

I still think spell casting should activate with a right-click and exiting the spell could be done with left-click, pressing Escape or through a UI icon.

Blizzard does the same thing. I used autoplay to get out.

Does anyone else have problems with Fireball not casting? I have had many experiences with selecting the spell, waiting for the charge to take place, and then the mana is gone but I never get to cast it.