Never had a problem, I never seem to have problems like this. I doubt it has anything to do with superior computer Knowledge because I believe I know sweet fuck all compared to what I would like to know and understand.
But as a rule, Ive always run clean installs when expansions come out. Just back up config files and saved games etc. I like to clean the registry of any and all useless entry's as well. I tend to blame the OS for most peoples problems. With the right tweaking or outright modding one can achieve almost total buglessness.
(Custom Windows Server 2003) I hate microsoft, but there a necessary evil for the moment. But making my own custom installs of Server 2003 I can at least fool myself into thinking I'm not relying on them by removing all of the shitty little windows logo's etc..
But anyway, my apparent luck with this game doesn't erase the real problems with this game.