[Plugin: MailChimp Widget] Doesn't work after switching hosts

Hi. I’m using your widget so people can sign up to receive an e-newsletter. So just a text field to enter email and a submit button. I had to switch hosts because I needed a static IP. I was on a Linux server but now on a Windows one. Now it’s not working. I’m also having problems with a forms plugin but my eShop is fine. I’m thinking a STMP problem? Any thoughts would be appreciated. Thanks…

http://wordpress.org/extend/plugins/mailchimp-widget/