Fields deleting when validation error occurrs

Hi,

On my contact form, all of the fields are deleting if the customer tries to submit the form and misses a required field. This doesn’t occur every time, but does occur on the first attempt. Is there any way to stop the fields disappearing and only show the field that hasn’t been filled in?

The link to my contact form can be found below:
http://www.tasgas.com.au/connect/apply/

Thanks

http://wordpress.org/extend/plugins/contact-form-7/