Problem with heading_title on checkout

Hi, I'm new to OC, using Version 1.5.5.1. When I checkout on page

http://www.domain.com/index.php?route=checkout/success in my test store the page shows

heading_title

Your order has been successfully processed!



Is there someplace in a template file or language file where I can fix this (hard coded wise) until I can figure out why it is happening? Thanks

it's supposed to be in the language file.

add $_['heading_title'] = 'MESSAGE YOU WANT';

to the language file

Thanks..will try that.