Indian geek pythonista <3 vim & Linux.
I had network issue with my Ubuntu 12.04 machine. It was able to fetch IP from DHCP but It was incapable to connect to outside world. I pinged google.com using its IP successfully but failed using domain name. It was obvious, something is wrong with DNS!
Linux uses /etc/resolve.conf as a DNS resolver library, a plain text file with dns entries. like nameserver 8.8.8.8
Ubuntu no more use /etc/resolve.conf however, it needs to specify dns entry in /etc/network/interfaces as
dns-nameserver 8.8.8.8
and then restart network-manager.