Fatal error when accessing MailChimp Integration plugin settings

Error: Fatal error: Cannot redeclare class Mailchimp in /home/annasfriends/public_html/dev/wp-content/plugins/mailchimp-sync/mailchimp-api/Mailchimp.php on line 17

Request: http://dev.annas-friends.com/wp-admin/options-general.php?page=mailchimp

I have an existing MailChimp Subscribe plugin installed, if that makes a difference.
Thanks, Morgan