When I play several turns in FreeOrion 0.3.8 (Windows Vista 32-bit, Core2Duo 2.13 GHz, 2 GByte RAM) the enemy empire order calculation is taking more and more time from turn to turn.
Once I looked on my watch and it took more than 2 minutes.
But I can speed it up by save and then load the savegame before I end my turn without restarting FreeOrion. If I do so, only the "production and growth" calculation is taking a moment, but the enemy empire orders are fast as lightning again. But only for once, if I do not save and load this savegame it is taking ages again.