If you're using custom game interface, DO NOT use this method
" [FrameDef]
LOADING_LOADING=<Text Here>
LOADING_PRESS_A_KEY=<Text Here>
LOADING_WAITING_FOR_PLAYERS=<Text Here>" etc, since, like Billy the Cat says, you will have problems with the changes made to game interface. To be more exactly, if you use that method, every change made trough "Game Interface" won't work.
The best way to change the loading screen texts if to open your map in NewGen WE, and the option of changing the text will be available in "Game Interface"