MailChimp plugin sending 2 confirmation emails?

I have my MailChimp plugin set up to automatically send out an email to a newly-registered user, asking the user to sign up for my mailing list. Unfortunately, MailChimp ends up sending 2 identical confirmation emails. I chatted with a MailChimp rep and they said it's the plugin's fault.

Any ideas?

Thanks. You guys always rock.