[Plugin: Visual Form Builder] Submit Button goes to Invalid URL

I’ve set up a form and it was working last week, however now when you click on submit it goes to a page which says:

Web Address

__________________

Not a Valid URL

This error was coming up when I had selected to just display a message. I set this up to redirect to a specific wordpress page instead but the same error still comes up. Do you have any ideas how to fix this?

I have 2 forms on the same wordpress site which are both generating this error: http://extra.microscooters.com.au/au-account-application/

http://wordpress.org/extend/plugins/visual-form-builder/