index.php tries to redirect you from the url you entered to the url that you specified in config.php. On some server setups, this seems to result in an endless loop.
Try to remove the complete "if" block in index.php that starts with
PHP Formatted Codeif (isset ($HTTP_SERVER_VARS['HTTP_HOST'])
i.e. all the lines between require_once('lib-common.php'
; and $display = ''; and see if that helps.
We're trying a different approach in Geeklog 1.3.8rc1, btw ...