Ask HN: How can a slot machine glitch?
Underflow. The price money of $42,949,672.76 is 20 cents short from 2^32 cents.
The Iowa case apparently (http://www.chicagotribune.com/news/local/breaking/chi-iowa-c...) was also close to that ($41,797,550.16), but quite a bit further off. I still would guess underflow to be the problem, though.