I have played a number of  games where the "End Turn" disappears after all moves are done.  I've waited for several minutes to see if the AI was doing something, but alas, I end up losing the game.  I've tried reloading from a previous save, closed the program and reopened it, even robooted the computer.  It seems that once a game has this happen it "game over!"
Any ideas?
I'm running a:
AMD 64  3200+  
1 gb Ram
Geforce 6600 w/ 256 mb Ram
Nvidia 81.98 drivers