Please add support for installation to ovz-ubuntu-11.10-x86_64.
Virtualmin only supports the Ubuntu LTS releases. To use the automated installer, you’d need to use either Ubuntu 10.04 or 12.04.
Note that Ubuntu 11.10 will be reaching it’s end of life in 2 months (in April 2013)… so even if Virtualmin did add support for that version, by the time the support was added, that distro version would be out of date
You could always upgrade that distro to 12.04 using Ubuntu’s upgrade feature, that would bring it up to 12.04.