Sorry -- I should have posted what lines needed to be changed.
Please make a backup copy of your "product_listing.php" file, in case I screw something up for you (or as long as you're using a custom/overrides folder you can just delete/replace the custom file if you need to).
In that file you want to look for "zen_clean_html" (no quotes). It appears in two places -- should be lines 98 and 100.
In line 98 where it says:
$lc_text = '<h3 class="itemTitle"><a href="' . zen_href_link(zen_get_info_page($listing->fields['products_id']), 'products_id=' . $listing->fields['products_id']) . '">' . $listing->fields['products_name'] . '</a></h3><div class="listingDescription">' . zen_trunc_string(zen_clean_html(stripslashes(zen_get_products_description($listing->fields['products_id'], $_SESSION['languages_id']))), PRODUCT_LIST_DESCRIPTION) . '</div>' ;
you want to remove the "(zen_clean_html" (note the parenthesis at the beginning); then remove one of the three closing parentheses after "['languages_id'])))", so there will be two not three: "['languages_id']))"
Do the same thing on line 100.
Let me know if this was unclear at all, or if it doesn't work for you.