Hi Simon,
With the Javascript disabled for the form I am able to see and submit the form on all pages of the site in both Chrome and Firefox, however I'm getting the "Cheatin’ huh?" error page. I'm going to need to continue to look into different scenarios which cause this error page, however one thing I would suggest doing is uninstalling, completely removing all plugin files, and reinstalling the plugin in WordPress. Doing a complete reset this way may resolve the current issue, but regardless I'm going to continue to work on getting to the bottom of this for you.
Thanks for your patience, Simon!
-Kath