Cant zoom
Cant think of why this would happen, but a slight work around while you wait for someone to solve the problem you are having would be to bind zoom in and zoom out to some buttons in the control options so you can skill use them. Not the best solution but atleast you will still be able to to do it.
SAME!
MAC OSX
thought that it was the mouse – however it works outside of the game. i can reassign the bindings to mouse 3, but i have to click the scrollto zoom out (not back in)
since patch!
Try to go into the options menu and disable the “Use scrolling gestures to change direction” option, this should re-enable the mouse wheel’s input