You did not extract in the SimCity folder did you?
You should not extract to the SimCity folder (or SimCityData)
It should be in a folder for itself, for example on the desktop .. It finds SimCity automatically ..
If your /SimCityData/Locale folder has two locales, delete one of them (the new locale)
Just saw your message. Nope I did just have it on the desktop but for some reason it worked today so it's all good!