Well, it is more than likely too late to ask your host to downgrade back to PHP 5.2.17. It is (in my opinion) not difficult to upgrade to the latest version. To upgrade from 1.3.8 it would be best to do the rebuild so that the plugins that are needed to continue to support your business are installed as up-to-date/verified operational as possible. Also would want to probably find an updated template as templates that worked with earlier versions of ZC need at least modification to continue working in newer versions. At this point it could be better to start with one that is already designed to work with the recent version of ZC.
Rebuilding by the above link will allow you to keep your existing database, users, products, etc... but operate more securely and at the this point more completely.
Make backups of the files and the database (these are two different things).
Make sure you have at least some of the suggested tools (or type of tool) that is provided here:
https://www.zen-cart.com/content.php...-with-zen-cart
Compare the original copy of your ZC version (1.3.8a) to what you have for your store to tell what was modified. That way if the changes need to be on your new site you will know what to change. A copy can be found at:
http://www.zen-cart.com/getit
Essentially you will be installing ZC again; however... AND THIS IS IMPORTANT... 1) Do
*not* delete your database by installing the new site over the old one while trying to start this upgrade/rebuild. 2) Again do
*not* put your store in maintenance mode while starting this upgrade/rebuild, 3) Do make backups as you go along, but specifically
*backup* your live database before the first time you run zc_install...
If upgrading to ZC 1.5.4. Also take a look at the
known issues with ZC 1.5.4 so that when the problem appears you know exactly how to correct it.
A few other helpful links for starters include:
A blank page or partially blank page is displayed.
An error has occurred please refresh the page and try again
Admin password doesn't work/needs to be reset/etc...
Hopefully that will help if you choose to do the upgrade on your own or whomever you get to help needs a little assistance.