Thanks Matty, I have a support ticket entered to my Hosting provider .... but as I was checking to make sure the email address of the domain was the one in use in the Subscribe2 settings, I decided to try registering another one of my emails. The first one I tried was the one I was already subscribed with, and subscribed2 replied that I was already subscribed, so that part works. Then I tried another email address and received the error message... then, when I went to look at the list of subscribers, of which my first email address was already confirmed as being on it... there weren't ANY subscribers. the list is empty, even though subscribe2 told me I couldn't use an email that was already subscribed.
any ideas why this would happen?