Im with Ubuntu 12.04 - Dell Inspiron 5110 (8g ram, i7 cpu). When I connect to a router at my place, i get an internal IP i can ping others in the network (and the router), but have no internet. I trided by checking with trough FF, IE and Opera and couldn't load any pages. I read all other similar topics and nothing helped.
Check if DHCP server is giving you nameservers. In terminal window type:
If not, the simply solution is adding nameservers by hand. However, if you experience this, you have a problem in DHCP Server.