try this:
1- in webmin go "Servers" >> "Apache Webserver" >> "Global Configuration" >> "Configure Apache Modules"
2- then make sure that there is a check in "suexec", also check "actions" (as webmin might complain about this one next)
3- then click "Enable Selected Modules" at the bottom of the page
4- then re-check and refresh virtualmin configuration

that is all i had to do to get mine working

The error is:

A problem was found with your Postfix virtual maps : No map sources were found in the Postfix configuration

It has nothing to do with bind or apache or anything else.

Google will help you with this error.