DNS Zone Error
Virtualmin is configured to setup DNS zones, but this system is not setup to use itself as a DNS server. Either add 127.0.0.1 to the list of DNS servers, or turn off the BIND feature on the module config page.
So I added 127.0.0.1 to the list. I then applied the configuration. I checked again and it gave me the same error. I took a look at the list again and found that all the changes that I made a minute or two before had been erased. I tried again with the same result.
I tried to edit resolv.conf manually, but the same exact thing happened.
That sort of thing can happen if another program is changing your resolv.conf file back to what it was — such as DHCP.