I'm getting the same error. Just hangs with 'adding email address', even if I don't enter an email address into the form.
Site is here:
http://new.ronadamsentertainment.com/When I turn on error reporting, this shows up in the module itself, before submitting anything.
Strict Standards: Only variables should be assigned by reference in .../modules/mod_s5_mailchimp_signup/tmpl/default.php on line 17