Another thing to remember about the game, is that it does not do very well at "house-keeping", as far as game resources go. So if you did a Submarine School mission, and then went into a Career without having shut down the game and then re-started it, then the game may have "corrupted" itself - or rather, it's Windows memory assignments... Think of each menu item, other than "Options", as a separate game "mode" that is separate from the other "modes"...but even a change in certain of the Options choices requires a game re-start to be set...
