Researched it but couldn't cast because I didn't have a water shrine. Captured a city that had one, hit next turn, and BSOD. Rebooted and tried to load the most recent save but the game says it has a problem and needs to close. Pretty sure the save was just after I got the city.
debug.err http://pastebin.com/SRVXPKt9
crash zip file from the load-crash http://dl.dropbox.com/u/8928343/Elemental1_08-2010-09-23T22-01-31-187.zip
save game http://dl.dropbox.com/u/8928343/QuickSave%20magic.EleSav