This issue has been fixed already in the 3.0.5.1 release. Run the followng commands on your server to update it to 3.0.5.1:
Code:
cd /tmp
wget http://www.ispconfig.org/downloads/ISPConfig-3.0.5.1.tar.gz
tar xvfz ISPConfig-3.0.5.1.tar.gz
cd ispconfig3_install/install
php -q update.php