The funniest bug I've ever encountered in Heroes is when your money gets reset to zero. In one very long and complex game (the map was created by some Englishman), I accumulated a lot of money. The amount went into the millions, or even billions. And then, one day, after a turn, the amount became negative. I couldn't buy anything. I couldn't accumulate more either (either there was a large negative number, or a small one, but it was growing in the negative direction). I barely managed to get out of the situation. I had to buy resources: wood, ore, etc.