Sailing a great merchant half-way around the world in order to bring in a huge pile of cash, then starting a golden age, thinking that the computer would somehow UNDERSTAND that I wanted to use the two useless great artists siting at home to start the golden age rather than the great merchant...
Ah, I remember when I did a similar blunder. When using 2 GP to start a GA, they actually have to be DIFFERENT types of people, doh! I remember getting stuck with 2 worthless great artists just rotting away...