The key is To update Incorrect

Feb 19, 2014 at 7:43 AM
Edited Feb 19, 2014 at 8:16 AM
I use Captcha MVC(version 1.4 ) in modal form (call by ajax)

when my forrm closed and open agin when click on refresh button it raise error

The key is To update Incorrect

what is wrong?
I Test it in IE10

Update
i sometime get this error
What is going to say this message , and when occure?