I came to this site some time back to report that I had taken three (3) polygraph tests, by two different operators, and all reported that I failed the test (deceptive).  These were controlled question tests (CQTs).  Recently, a new polygraher was recommended highly, and I went for yet one more test.  I told him the background, but he didn't have the earlier results.  He suggested trying a directed-lie test.  Result:  I passed with a very high truthful score.

I am a pretty simple guy, and I believe in myself and the idea that right wins in the end.  If you were wondering, I made no effort to fool the machine in any of the tests, and the questions were always about the same.

I can't offer much insight into why things went this way, except for one nagging thought.  On the CQTs, I thought I was actually tellling the truth on the control question, and at least as I remember, the operators didn't tell me I was supposed to be lying.  I am led to believe that being too honest works against you in a polygraph test.