mamabird31 on "[Plugin: Easy Sign Up] Security error"

I just added this widget to my website with no modifications. I tried it both with the short code and with the widget. When I submit the form I get a blank page with only these words: "Failed Security check - are you a robot?" I can't find anything on this anywhere. The url parameter for that error page is ?esu_qv=true if that helps.

Thanks!

http://wordpress.org/extend/plugins/easy-sign-up/