I actually ran into a similar problem not too long ago. Not sure if the same issue on the windows version, but I found that while using the scrollwheel of the mouse to scroll up and down through the different setting fields, what ever drop-down your cursor passes through will automatically change the options in that field (without clicking to activate). I unknowingly changed the type of camera used in the scene and didn't think to look at my settings when initially troubleshooting.
Just my experience....hope this helps.
Good luck