We had this problem yesterday when several of our booked activities, including Palo Brunch suddenly disappeared from our "Plans". The customer support people I talked with said it's a known problem and IT has been working on it. Reading this thread, I realize that it's been going on a week.
As a former IT manager, I realize these glitches sometimes happen. The fact that the company hasn't devoted enough resources to fix the problem quickly indicates to me how low Disney has dropped customer service and satisfaction down their list of priorities.