Mailchimp Error in Sub-blog only

I have a mailchimp sign up form in the sidebar of my front page, and also in a sub-blog. The front page is fine, but there is an error on the sub-blog.

It asks me to re-run the MC set-up under the settings menu. When I do, I get this error:

Warning: Invalid argument supplied for foreach() in /home/housings/public_html/wp-content/plugins/mailchimp/mailchimp.php on line 352