Well, I hate to go against what DH Support tells you, but I think they missed the boat on this on. ALL my domians running Joomla, including the "test* that I set up this morning run PHP-CGI. In fact, if you use the “one-click” install (which I did this morning to test your circumstances), it tells you on the web panel that your domain will be set to PHP-CGI for the one-click install.
I think the next thing I would do would be to run a small php program from my home directory, while the domain is set to use PHP-CGI, to get the PHP information.
Simply put the following single line of code in a text file, name it “phpinfo.php”, then place it in your root web directory of your domain:
<?php phpinfo(); ?>
THen “run” that program by going with your browser to http://www.yourdomain.com/phpinfo.php. This will run a program that will show you all kinds of useful stuff about PHP as it is running on your server, and that will help us figure out what is going on here.
In all my domains, running on PHP-CGI, phpinfo shows that session.save_path is set to /tmp which is writable on all my servers.
I suppose it is possible that your server is misconfigured on the DH end, though I believe that to be unlikely. I am assuming that you are running PHP 4 as PHP-CGI, on a “standard” configuration DH server…the output of this program will confirm all of that, or indicate any deviation.
I personally suspect that you may have a stuck cookie or a browser cacheing problem, which seems to me to be more likely to cause a looping condition at login.