I had this glitch/error after modding as well. I had been having problems with getting the .zips to turn back into .paks. After changing the settings under Tools>Folder Options>View>Hide extensions for known file types, I found that my english_xml.pak was actually english_xml.pak.zip. (Under the Localization folder) After I changed it, all text came back when I loaded the game once again. Cheers