When starting the game, the cursor position and the actual position where the game sees the mouse pointing are not the same, i tried a few resolutions and it seems that:
At my native resolution (Full HD 1920x1080) they are the same.
At 1600x900 actual is slightly to the right and down to cursor.
At 1280x720 actual is even more to the right and down to cursor than at higher resolutions.
Im playing Fullscreen Mode.
I think it's got something to do with the game not being able to resize its own UI when the resolution is not screen native.
SOLUTION: Very simple, minimize/switch tasks/etc. and then switch back to the game.