I've looked at your site and have never seen a nproblem quite like this one before. In Zen Cart terms in case other Zen Carters have seen this and have something to add ... on your product_info page the contents of the "add to cart" box have been replaced the words "contact us" in your site's language and a link to the "contact us" page.
In the meantime, could you find the tpl_product_info_display.php file for the template that you are using ("Classic" I suspect) and post the lines between the comments <!--bof Add to Cart Box --> and <!--eof Add to Cart Box-->. Also which version of Zen Cart are you using?