I have had a similar issue--- looks like the same as Imadot, where I thought the tilde key stopped working, but in fact it actually hasn't. It was just a setting somewhere change that my 'expanded' view was the same size as the normal view.
To fix, I log into aces high, get into the tower, press the tilde key to go to 'expanded view' (even though nothing happens), then I 'resize' the window. Then once I press the tilde key to return to normal size it would work properly. This happens every few months or so.
Hope this helps, maybe.