Confirm no other application is running on port 53.
Open a Terminal (Applications -> Utilities) an type the following:
netstat -na | grep "\.53"
If in the output is similar to:
tcp6 0 0 *.53 *.* LISTEN
then another application (eg. another DNS) is using this port.
BIND log file
Check your BIND log file for any information regarding why DNS is not starting. The log file of BIND (name server) is located at "/var/log/named.log".