I assume the movie is actually 59.94 not 60 FPS (if so the value in Twixtor for Input FPS should be 59.94). It shows as 59.94 in the project bin...
And I assume your comp is something else, e.g. 29.97 or 25 yes? and the rate you are rendering to?
Would be best you simply enter your email here: http://revisionfx.com/support/contact/
And the automatic response will send you info on how to upload an example (with your AE project) so we can look at it