[Plugin: CATS_JobSite] validation error

When I apply for a job, and fill out all fields correctly, I get the following error:

“Missing filed
One of the fields on the previous page was required and left empty. Please click on the back button on your browser and complete all required fields and try again.”

I do however get a confimation mail of my application.

You can test this yourself here:
http://www.searchworkx.nl/vacatures

http://wordpress.org/extend/plugins/cats-jobsite/