I was using the gpl virtualmin, worked fine (for a newb). uninstalled it, bought pro, executed the install.sh, no virtualmin in the webin server list.
1st time I tried the install, I saw an 'fatal error' stating that some group or another wasn't found... before I could write it down the script finished and closed the putty window. I did disable a lot of groups that the system wasn't using (it started as a game server... now I want to try out some webhosting), so I'm sure that's the problem... but I don't know which to re-enable.
2nd/3rd time I tried it, it said virtualmin was already installed and a bunch of other stuff, then exited. I couldn't scroll back up to tell what was going on.