I have seen some questions similar to mine but not the same. I have just gone through the process of installing 12.04 dual boot with WIndows 8. Before I resolved all my boot issues and ran ubuntu I could connect to the internet no problem. Now I can connect to my router and ping is OK, but no applications can reach the internet. pinging google fails.
On a similar user question someone suggested pinging 22.214.171.124 That does work.
I think this went bad for me when a large number of updates were installed.