I have installed Virtualmin following the instructions outlined at: http://www.virtualmin.com/download.html#gpl
Everything appears to be running correctly (although I had to adjust some postfix settings after installation to get it to work). It has been installed on an Amazon Web Services (AWS) instance which has a fresh install of CentOS 5.6.
However, the Webmin and Usermin services are not started on boot. I checked the Webmin Bootup and Shutdown module, and their are both set to start. Also, I can not find any errors in log files on the system.