Contact Form and Upgrade

I just upgraded to the latest version of wordpress. I decided to install a new contact us form, the Dagon Desings script. The problem is that after an email is sent to me, it goes back to the same page, with the same header telling people how to contact me, and that I will try to answer within 24 hours. Below this, it says your message has been received.

My old contact form had different text after the messge had been sent, you did not see the same instructions. My question, how can I change the language on the contact form to say something entirely different after the message is sent?

By the way, redirecting to another page is not an option. It worked fine in Firefox, but IE gives an error page. I have been up all night trying to figure this out, so any help is appreciated.