You have something running a DNS server on port 53 already.
From terminal - do a "netstat -a" then find what process is using that port.
OK, I ran that and I can't see anything. Sorry it is quite long - am I missing something on there or looking int he wrong place?
Proto Recv-Q Send-Q Local Address Foreign Address (state)
tcp4 0 0 192.168.0.12.57206 artemis.ssh.only.http ESTABLISHED
tcp4 0 0 192.168.0.12.57205 199.16.156.21.http ESTABLISHED
tcp4 0 0 192.168.0.12.57204 68.232.35.139.https ESTABLISHED
tcp4 0 0 192.168.0.12.57192 edge-star-shv-03.http ESTABLISHED
tcp4 0 0 192.168.0.12.57191 lhr14s20-in-f15..https ESTABLISHED
tcp4 0 0 192.168.0.12.57190 a23-66-242-110.d.https ESTABLISHED
tcp4 0 0 192.168.0.12.57189 95.100.97.129.http ESTABLISHED
tcp4 0 0 192.168.0.12.57188 lhr08s01-in-f2.1.https ESTABLISHED
tcp4 0 0 192.168.0.12.57187 wb-in-f84.1e100..https ESTABLISHED
tcp4 0 0 192.168.0.12.57186 95.101.239.139.http ESTABLISHED
tcp4 0 0 192.168.0.12.57085 157.56.251.217.https ESTABLISHED
tcp4 0 0 192.168.0.12.56688 lhr08s02-in-f22..https ESTABLISHED
tcp4 0 0 192.168.0.12.54963 we-in-f109.1e100.imaps ESTABLISHED
tcp4 0 0 192.168.0.12.54812 we-in-f109.1e100.imaps ESTABLISHED
tcp4 0 0 192.168.0.12.54618 192.168.0.8.afs3-files ESTABLISHED
tcp4 0 0 192.168.0.12.daap 192.168.0.8.49304 ESTABLISHED
tcp4 0 0 192.168.0.12.daap 192.168.0.8.49290 ESTABLISHED
tcp4 0 0 192.168.0.12.daap 192.168.0.8.49289 ESTABLISHED
tcp4 0 0 192.168.0.12.52834 we-in-f108.1e100.imaps ESTABLISHED
tcp4 0 0 192.168.0.12.49751 wg-in-f125.1e100.jabbe ESTABLISHED
tcp4 0 0 localhost.57343 *.* LISTEN
tcp4 0 0 192.168.0.12.54821 17.149.36.183.5223 ESTABLISHED
tcp4 0 0 192.168.0.12.51979 17.172.34.99.imaps ESTABLISHED
tcp4 0 0 192.168.0.12.50311 wi-in-f109.1e100.imaps ESTABLISHED
tcp4 0 0 192.168.0.12.65139 do-2.lastpass.co.https ESTABLISHED
tcp4 0 0 192.168.0.12.63943 199.16.156.81.https ESTABLISHED
tcp4 0 0 192.168.0.12.63826 199.16.156.81.https ESTABLISHED
tcp4 0 0 192.168.0.12.60223 wg-in-f125.1e100.jabbe ESTABLISHED
tcp4 0 0 192.168.0.12.59874 p06-imap.mail.me.imaps ESTABLISHED
tcp4 0 0 192.168.0.12.59689 17.172.34.111.imaps ESTABLISHED
tcp4 0 0 192.168.0.12.59662 17.172.238.205.5223 ESTABLISHED
tcp4 0 0 192.168.0.12.59630 108.160.162.46.http ESTABLISHED
tcp6 0 0 imac-406c8f1ca82.daap fe80::7256:81ff:.52063 CLOSE_WAIT
tcp6 0 0 imac-406c8f1ca82.daap fe80::7256:81ff:.52042 CLOSE_WAIT
tcp4 0 0 192.168.0.12.52229 192.168.0.73.ms-wbt-se ESTABLISHED
tcp4 0 0 *.63185 *.* LISTEN
tcp4 0 0 *.63098 *.* LISTEN
tcp4 0 0 *.63043 *.* LISTEN
tcp4 0 0 *.63031 *.* LISTEN
tcp4 0 0 *.63030 *.* LISTEN
tcp4 0 0 localhost.62054 localhost.62056 ESTABLISHED
tcp4 0 0 localhost.62056 localhost.62054 ESTABLISHED
tcp4 0 0 localhost.62054 *.* LISTEN
tcp6 0 0 *.daap *.* LISTEN
tcp4 0 0 *.daap *.* LISTEN
tcp4 0 0 192.168.0.12.59978 192.168.0.73.microsoft ESTABLISHED
tcp4 0 0 *.https *.* LISTEN
tcp4 0 0 *.http *.* LISTEN
tcp4 0 0 192.168.0.12.49402 do-2.lastpass.co.https ESTABLISHED
tcp4 0 0 *.32469 *.* LISTEN
tcp4 0 0 *.globe *.* LISTEN
tcp4 0 0 localhost.49303 localhost.49301 CLOSE_WAIT
tcp4 0 0 localhost.26164 localhost.49201 ESTABLISHED
tcp4 0 0 localhost.49201 localhost.26164 ESTABLISHED
tcp4 0 0 localhost.26164 *.* LISTEN
tcp4 0 0 *.17500 *.* LISTEN
tcp4 0 0 *.32443 *.* LISTEN
tcp4 0 0 *.32400 *.* LISTEN
tcp4 0 0 localhost.4380 *.* LISTEN
tcp4 0 0 localhost.4370 *.* LISTEN
tcp4 0 0 localhost.acmsoda *.* LISTEN
tcp4 0 0 localhost.6971 *.* LISTEN
tcp4 0 0 localhost.64022 *.* LISTEN
tcp4 0 0 localhost.6970 *.* LISTEN
tcp4 0 0 localhost.12311 *.* LISTEN
tcp4 0 0 localhost.6968 *.* LISTEN
tcp4 0 0 localhost.ipp *.* LISTEN
tcp6 0 0 localhost.ipp *.* LISTEN
udp6 0 0 *.56530 *.*
udp4 0 0 *.56530 *.*
udp6 0 0 *.59101 *.*
udp4 0 0 *.59101 *.*
udp4 0 0 *.59381 *.*
udp4 0 0 *.50623 *.*
udp6 0 0 *.57923 *.*
udp4 0 0 *.57923 *.*
udp6 0 0 *.57887 *.*
udp4 0 0 *.57887 *.*
udp6 0 0 *.63011 *.*
udp4 0 0 *.63011 *.*
udp6 0 0 *.59147 *.*
udp4 0 0 *.59147 *.*
udp6 0 0 *.54859 *.*
udp4 0 0 *.54859 *.*
udp6 0 0 *.57456 *.*
udp4 0 0 *.57456 *.*
udp6 0 0 *.63876 *.*
udp4 0 0 *.63876 *.*
udp6 0 0 *.53246 *.*
udp4 0 0 *.53246 *.*
udp6 0 0 *.61535 *.*
udp4 0 0 *.61535 *.*
udp6 0 0 *.58306 *.*
udp4 0 0 *.58306 *.*
udp6 0 0 *.60380 *.*
udp4 0 0 *.60380 *.*
udp4 0 0 192.168.0.12.52462 *.*
udp4 0 0 localhost.59110 *.*
udp4 0 0 192.168.0.12.57148 *.*
udp4 0 0 localhost.61047 *.*
udp4 0 0 *.32413 *.*
udp4 0 0 172.16.149.1.ntp *.*
udp4 0 0 192.168.238.1.ntp *.*
udp4 0 0 *.62948 *.*
udp4 0 0 *.domain *.*
udp6 0 0 *.55498 *.*
udp4 0 0 *.55498 *.*
udp6 0 0 *.56669 *.*
udp4 0 0 *.56669 *.*
udp4 0 0 *.55851 *.*
udp4 0 0 *.51923 *.*
udp4 0 0 *.8094 *.*
udp4 0 0 *.10322 *.*
udp4 0 0 *.5197 *.*
udp4 0 0 *.ssdp *.*
udp4 0 0 *.32410 *.*
udp4 0 0 *.32414 *.*
udp4 0 0 192.168.0.12.63053 192.168.0.1.nat-pmp
udp4 0 0 *.17500 *.*
udp6 0 0 *.55035 *.*
udp4 0 0 *.55035 *.*
udp4 0 0 *.57083 *.*
udp4 0 0 *.* *.*
udp6 0 0 *.52826 *.*
udp4 0 0 *.52826 *.*
udp4 0 0 *.* *.*
udp6 0 0 *.53484 *.*
udp4 0 0 *.53484 *.*
udp6 0 0 *.64086 *.*
udp4 0 0 *.64086 *.*
udp6 0 0 *.56793 *.*
udp4 0 0 *.56793 *.*
udp6 0 0 *.54818 *.*
udp4 0 0 *.54818 *.*
udp6 0 0 *.54096 *.*
udp4 0 0 *.54096 *.*
udp4 0 0 *.* *.*
udp4 0 0 *.* *.*
udp4 0 0 *.* *.*
udp4 0 0 192.168.0.12.ntp *.*
udp6 0 0 imac-406c8f1ca82.ntp *.*
udp6 0 0 localhost.ntp *.*
udp4 0 0 localhost.ntp *.*
udp6 0 0 localhost.ntp *.*
udp6 0 0 *.ntp *.*
udp4 0 0 *.ntp *.*
udp6 0 0 *.mdns *.*
udp4 0 0 *.mdns *.*
udp4 0 0 *.* *.*
udp4 0 0 *.* *.*
udp4 0 0 *.* *.*
udp4 0 0 *.* *.*
udp4 0 0 *.* *.*
udp46 0 0 *.* *.*
udp4 0 0 *.netbios-dgm *.*
udp4 0 0 *.netbios-ns *.*
icm4 0 0 *.* *.*
icm6 0 0 *.* *.*