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.
This sounds exactly like a DNS problem. In order to really fix your problem though you really out to have stated what desktop environment you are using because some desktop environments like KDE have their own slutions to problems like this. Since you didn't state which one you are using I'm going to assume you are using Unity(since it's already installed by default).
First off, check with any other program that you have installed uses the internet, like a game etc. and see if that program/game can indeed access the internet. If it can even though Internet browsers "cannot", it might even be as simple as a proxy being set on when you don't need to use a proxy. In your browsers settings try turning off proxys and see if that solves the issue.
If not, then it could in fact be a DNS problem. I suggest opening the Terminal and type: dpkg-reconfigure resolvconf and see if that solves your problem.