What build of Asterisk are you using.
Are you using VIOP with no other trunks (and if this is the case you can stop reading now and beat yourself over the head with a blunt object until you lose consciousness)
are you using the same router to connect to the internet as you are to connect to all the extensions?
Are you using physical extensions or are you using soft phones
If soft phones, which?
What TDI are you using?
It's trying to resolve DNS and failing/timing out.
You need to either run a local name server on the box, or, ensure /etc/hosts has mappings for all the IP's on your LAN and hosts you refer to.
It's needs to be able to reverse lookup all IP's of phones that register to it, so have hosts like:
192.168.1.11 phone1
192.168.1.12 phone2
etc.
If you register to other hosts, you may also need:
196.1.2.3 other.host.com
N.B. This is not ideal in that you'll override what's in the DNS. Better may be to run a local DNS instance with just a hint for the remote host names.