Game not recognizing my advances and allowing units to be built?

[BYUTonyKnight]

I've never had this happen before, but all of a sudden in the middle of a game it just won't seem to allow me to upgrade or built units I should be allowed to be building like tanks, battleships, etc. I've tried quitting and re-starting, but it seems to be stuck in that spot. It's like it hiccuped at a certain point and stopped letting me build new stuff as I've advanced. Any way to fix this?? I'd hate to kill an otherwise masterful game that I've been looking forward to winning - have the French and the Chinese on the run!