UTF8 error in browser

I have designed a PDF form designed in Livecycle designer. The form has a submit button which invokes a servlet. The servlet receives the request and send a response in "text/html UTF-8". If have no browser or IE open when submitting the form, I receive a response that the form has been either successfully submitted or not. However, if I have Firefox open when Submitting, I get an Adobe Reader dialog box that says "An error occurred during the submit process. Cannot process content of type text/html utf-8".
When I look in the database, the form is successfully submitted. How do I make the adobe pop up to disappear and print the confirmation.