Why is the event saying "Reached Max Capacity"!!!

Hi there.

I have just almost had a heart attack.

I am promoting a course far and wide. I have 1 person booked via the site (and then we had to move the date - so the event date was changed and it was moved and it has unlimited spaces - which should have been 20 (my fault) and the event was open.

I just tested it via a test login I have (subscriptions) and it is telling me "Sorry, the event has reached its max capacity."

WHY would this be happening????

Firstly, there were unlimited spaces.
Secondly only ONE person has booked online (and I was directly someone else to use the online booking feature only to test and get this message and almost die). I have no idea how many people might have tried to book over past weeks.
Thirdly, is there some issue with moving the dates of courses (this is practical, this is what happens ESP as the plugin doesn't duplicate events you are left with changing the date.
Fourthly, what happens to people who have already booked for an earlier date and have moved with the new date. Is the system coping with such a change?

PLEASE someone check out why this is happening and how to fix it.

Thanks.
Karen