Just found a scoring bug (not sure if it is reproducible) in the latest Yahtzee version. http://jtrotman.tripod.com/yahtzee.html
If you get more than one Yahtzee and score it in one of the Joker sections, then press Options | Help, once you go back to the scoring, the bonus increases by 100. I kept doing this a few times and now my top score is 700+ ;-)
Can it be reproduced?