Sometimes when a page is showing up blank due to hidden PHP errors, it can be hard to track down the cause — especially if your server’s errorlog isn’t active or cannot easily be accessed.
Installing the attached debug error-logging tool will create debug logs of PHP problems for you to review.
Be sure to remove the utility when not needed, or it will slow down your site and consume large amounts of disk space. Click here to download : http://www.zen-cart.com/index.php?main_page=product_contrib_info&products_id=860