I just played with Ubuntu (on an OpenVZ container) and noticed this. This looks like a bug? I also noticed that the “Bootup and shutdown” sections shows “no” for all actions.
Maybe a result of “[1.534] minor version includes much improved support for the newly released Debian 6.0 (Squeeze) and Ubuntu 10.10, in particular in the Bootup and Shutdown … modules”. Or maybe it always looks like this in Ubuntu
Copy and paste:
Operating system Ubuntu Linux 10.04.2
Webmin version 1.534 Virtualmin version 3.83.gpl GPL
Theme version 8.0 Time on server 22/Feb/2011 01:30
Kernel and CPU Linux 2.6.18-194.26.1.el5.028stab079.2 on i686