I had also the XML errors when i started civ4, tried all off the solutions mentioned in this thread, nothing worked, still XML errors.
I also deinstalled civ4 and installed it again, still XML errors.
Then I deinstalled civ4 and deleted manually the remaining civ4 folders on my HD which where in "My Documents", "Documents and Settings" and the folder which I had Civ4 installed in "Civilization 4" (the default folder is "program files\firaxis\sid meier's civilization 4" I belief)
Installed again, no more errors, everything fine now.
I also deinstalled civ4 and installed it again, still XML errors.
Then I deinstalled civ4 and deleted manually the remaining civ4 folders on my HD which where in "My Documents", "Documents and Settings" and the folder which I had Civ4 installed in "Civilization 4" (the default folder is "program files\firaxis\sid meier's civilization 4" I belief)
Installed again, no more errors, everything fine now.