Virtualmin GPL will not install on clean CentOS 5.5 Server

Everytime I attempt to install virtualmin, i always get the exact same fatal error and it rolls back everything. Below is the out-put. Please tell me what is wrong.

INFO - Updating SpamAssassin rules... ...in progress, please wait... sa-update failed. Error (if any): 0

Displaying the last 15 lines of /root/virtualmin-install.log to help troubleshoot this problem:
Package dovecot-1.0.7-7.el5.x86_64 already installed and latest version
Package spamassassin-3.2.5-1.el5.x86_64 already installed and latest version
Package mod_dav_svn-1.4.2-4.el5_3.1.x86_64 already installed and latest version
Package cyrus-sasl-gssapi-2.1.22-5.el5_4.3.x86_64 already installed and latest version
Package cyrus-sasl-gssapi-2.1.22-5.el5_4.3.i386 already installed and latest version
Package 2:mod_ssl-2.2.3-43.3.vm.x86_64 already installed and latest version
Package ruby-1.8.5-5.el5_4.8.x86_64 already installed and latest version
Package ruby-devel-1.8.5-5.el5_4.8.x86_64 already installed and latest version
Package ruby-devel-1.8.5-5.el5_4.8.i386 already installed and latest version
Package rubygems-0.9.2-1.el5.noarch already installed and latest version
Package perl-XML-Simple-2.14-4.fc6.noarch already installed and latest version
Package perl-Crypt-SSLeay-0.51-11.el5.x86_64 already installed and latest version
Nothing to do
INFO - 2010-12-05 18:43:36 - /usr/bin/yum -y -d 2 install bind bind-utils caching-nameserver httpd postfix bind spamassassin procmail perl-DBD-Pg perl-DBD-MySQL quota iptables openssl python mailman subversion mysql mysql-server mysql-devel postgresql postgresql-server rh-postgresql rh-postgresql-server logrotate webalizer php php-domxl php-gd php-imap php-mysql php-odbc php-pear php-pgsql php-snmp php-xmlrpc php-mbstring mod_perl mod_python cyrus-sasl dovecot spamassassin mod_dav_svn cyrus-sasl-gssapi mod_ssl ruby ruby-devel rubygems perl-XML-Simple perl-Crypt-SSLeay: Succeeded.
INFO - 2010-12-05 18:43:36 - Updating SpamAssassin rules…
INFO - Rule updates failed

Is it possible that the server is behind some kind of firewall that prevents it from connecting to the spam assassin update servers?

Anyway, this kind of problem should not cause the whole installation to fail, or any roll-back to trigger, since the rules update can be done later too. If it turns out that this is indeed the reason and effect, you might want to file a bug report in the issue tracker.