Session information lost after login

I did a fresh install of Zen Cart 1.3.0.1 on a SuSE 10.1 server. Suse 10.1 is shipped with MySQL 5 by default, but I have downgraded to MySQL 4.1.19, downloaded directly from mysql.org.
I'm running php 5.1.2, no php4 packages are available anymore for suse 10.1.

After logging in, all session information is lost. The user is redirected to the index page and is not logged in. The shopping cart is empty. There is an additional user online according to zen cart.

This is the url to the shop: http://zencart.controlxs.com/
and the tech support file: http://zencart.controlxs.com/zc_install/techsupp.php

Hack away at your leasure, I'm going to delete this install as soon as the problem is solved anyway :-)

Have you tried deleting all the files in your shop directory and re-installing?

Zen Cart will write files to the directories that save your sessions if you check off the area that says to save sessions as files and not in the database.

If you chose to save sessions in the database, then you could possibly just re-upload the install directory and start from there.

I've had this problem before and a reinstall seemed to sort it out.