Could you tell me what's your php version and please turn on php debug. That will help troubleshoot what's going on.

I have the same problem after having chmodded all the files as directed. Here is what php debug shows when I try to update the config page but nothing saves:

Warning [PHP]: ob_start(): output handler 'ob_gzhandler' cannot be used after 'URL-Rewriter' in file include/cp_functions.php line 33
Notice [PHP]: Undefined index: current in file modules/webmailfx/class/tabs.php line 283
Notice [PHP]: Undefined index: current in file modules/webmailfx/class/tabs.php line 283

running PHP 4.3.8
mysql 12.22
FreeBSD 4.9
perl, 5.8.3

Could this be a redirect problem?