After I had the above referenced problem, I scoured for literally HOURS looking for the solution. Finally, I found it, and I am listing it here for those who might have the same problem. It is sometimes caused if you use a shared SSL, and the redirects somehow get corrupted. If you are certain that BOTH configure.php files are correct, try this! Log onto your server, and navigate to osCommerce/catalog/includes/functions/general.php. As with anything (but especially when working with php files), BACKUP, BACKUP, BACKUP. In case things don't work out, you can at least restore the original file. I can't take credit for this script, for I found it out of desperation. Lots of credit to the original author.