Had sovereign + one unit selected. Was doing nothing else but right click on spiders to move/attack, and ending my turn after I did so.
Edit: I guess I should note that this was after loading a saved game.
debug: http://pastebin.com/m5e742b18
dxdiag: http://pastebin.com/m3141f2d4
Fogbugz ticket:
http://fogbugz.stardock.com/default.asp?70475_lb76
