I can not cut this ngon in ortho mode, I attached the pic and the .blend.
I'm on win764 latest build.
It's very odd.
if i try this blend on r53194 (win32 buildbot) , load it with load ui enabled, cutting A to B does not cut anything as it is reported.
But if -before- cutting i press "Numpad ." (to center the view on the selection, that by default is the vertices named A and B) and cut A to B, cutting works without a problem.