Failed to open socket family 10 : Address family not supported by protocol at /usr/libexec/webmin/miniserv.pl line 557.
This is because you are trying to start Webmin on a system without IPv6 support.
sudo nano /etc/webmin/miniserv.conf
[root@vps0400 ~]# vi /etc/webmin/miniserv.conf ipv6=0 /etc/webmin/start
Stopping Webmin server in /usr/libexec/webmin
[root@vps0400 ~]# service webmin restart