[Plugin: FormBuilder] problem ! "You have already submitted this form data once"

hi. i get this messege after filling all the fields,
even if i change the content, change the ip, change the computer… it still alwais bring this error….

i have seen that people in this forum wrote about this and got no answare.

can you please help me with this ?

i use wordpress 3
php 5.3
mysql as new is it gets

this is the link to my site:
https://gadi.zeevm.co.il/?page_id=35

p.s.
do you have any kind of a guide of how to make a multi page contact form ? i will be very happy to have one because i’m getting some trable in this issue.

thank you