It would appear to be something specific to the host account. I have a sister site that is a near identical match to this one. I've made the same connection and security assist changes on that site, and it still works fine. I've attached both the page on the site with the problem (tbl_product_update.php), and the similar page from the sister site (tbl_product_update_works.php) that is working properly. Save for the addition of a field and corresponding code for that, the pages are identical.
However, I installed the page that works on the sister site onto the site with the problem, and it experiences the same freeze issue. Therefore, I think the problem exists outside the page itself.