DNS configuration on Ubuntu EC2

I created an Ubuntu 14.04 server instance on Amazon's EC2 (using AMI - ami-b141a2f5 ) running as a spot instance.

As soon as the instance is launched I can connect from my Mac using SSH to the elastic ip address.

However, I can't ping google.com or any other URI. I can't run apt-get, wget, curl, etc. All commands get 'hostname unresolved'.

I have used elastic ip (linked to VPC), Route 53 with a registered domainname and two rulesets:

ns-1620.awsdns-10.co.uk ns-250.awsdns-31.com ns-1338.awsdns-39.org ns-898.awsdns-48.net

VPC with: DNS Resolution = Yes, DNS Host Names - Yes,

and an unrestricted security group.

/etc/resolv.conf is empty.

Any ideas?

Thanks in advance!