Yep Pixxi, I could not say from the top of my head then. But at approx line 88 the price update part should be update to:
Code:
			if($_POST['product_new_price']){
				$_POST['product_new_price'] = zen_db_prepare_input($_POST['product_new_price']);
				foreach($_POST['product_new_price'] as $products_id => $new_price) {
					if ($_POST['product_new_price'][$products_id] != $_POST['product_old_price'][$products_id] && $_POST['update_price'][$products_id] == 'yes') {
						$count_update++;
						$item_updated[$products_id] = 'updated';
						$db->Execute("UPDATE " . TABLE_PRODUCTS . " SET products_price='" . zen_db_input($new_price) . "', products_last_modified=now() WHERE products_id=" . (int)$products_id);
						zen_update_products_price_sorter((int)$products_id);						
					}
				}
			}
Colored quote to highlight the actual change:
if($_POST['product_new_price']){
$_POST['product_new_price'] = zen_db_prepare_input($_POST['product_new_price']);
foreach($_POST['product_new_price'] as $products_id => $new_price) {
if ($_POST['product_new_price'][$products_id] != $_POST['product_old_price'][$products_id] && $_POST['update_price'][$products_id] == 'yes') {
$count_update++;
$item_updated[$products_id] = 'updated';
$db->Execute("UPDATE " . TABLE_PRODUCTS . " SET products_price='" . zen_db_input($new_price) . "', products_last_modified=now() WHERE products_id=" . (int)$products_id);
zen_update_products_price_sorter((int)$products_id);
}
}
}
Tested now, and it works as expected

I would like to update the quick_updates soon (and then the above fix will be included of course), but time flies.....

(
Note that this only updates the sort order for prices that are updated *after* the above change. If really needed, it's also possible to update the sort order for all prices without editting quite easily using this line zen_update_products_price_sorter((int)$products->fields['products_id']) in the while (!$products->EOF) loop. (but better remove this one again after all prices are sorted)
)