trying to access the file that generates the theme:
gives a 500 server error.
this is most likely due to a permissions problem.
Using an FTP program, log into your servers ftp , right click the galleries/ folder and select set permissions. Set the permissions to 755, make sure to have it recurse through all files and folders underneath it. I recommend using Filezilla for this:
also, edit the admin_gallery/common/properties.php file, change:
[php]$GLOBALS['permissions'] = array(
'dir' => 0777,
'file' => 0666
$GLOBALS['permissions'] = array(
'dir' => 0755,
'file' => 0755