I had the same problem today and stubled on the answer. Pretty easy too.
Click on the wireless connection icon in left lower corner or open the network connections icon. Click properties on the wireless connection... under internet protocol (TCP/ip) highlight it and click properties.
Make sure it says obtain IP address automatically. Write down the numbers you see before you do that just in case it doesn't work.
If it still doesn't work, try to set DNS to 126.96.36.199 and 188.8.131.52 (Google DNS).
Then see if a website like google comes up.
I hope that helps