Did you get a reminder to register for the August Dinner when your spouse had already registered you? It's because you were registered under your spouse's membership, so the system views you as a guest of your spouse and doesn't record your registration individually. The reminder to register messages are sent automatically to members who do not show as having registered. Your spouse should have received a confirmation when he or she registered, and as long as your name is listed on the confirmation, you are also registered.
Although we ask couples to register together in order to simplify the invoice process, this is an unfortunate side effect.