If you don't know what this error is, please see this link: http://forums.civfanatics.com/showthread.php?t=328959.
I have found no solution for this. I have uninstalled and reinstalled 4 times. I have deleted every possible reference to game between those installations.
I have heard that it is a glitch with Windows 7 64 bit (which I have), but I have seen no confirmation of that.
Help would greatly appreciated, as it effectively makes Civ 4 unplayable.