If the Error 404: Not Found message appears during an update, it will be necessary to do it manually:

cd /tmp

# for beta version
wget http://www.ispadmin.cz/update/update_ispadmin_ion_beta_AddHashHere.tgz

# for stable version
wget http://www.ispadmin.cz/update/update_ispadmin_ion_AddHashHere.tgz

tar zxfv DownloadedFile.tgz

cd ispadmin_update

./update.pl