I agree with lr4444lr: there is something going on that apparently only comes out when they meet you face to face. We do not know you so I will have to work on

I agree with lr4444lr: there is something going on that apparently only comes out when they meet you face to face. We do not know you so I will have to work on the little you put on the OP... maybe during the on-site interview you come out as a bit too desperate about changing job? or too whiney about the current job? Or both? Try to consider if this could actually be a factor: I am sure that "what do you think of your current position" is pretty much a criteria in considering a new hire, even if it is not necessarily prominent during the interview.