I had this same problem with a Dell Inspiron 15, with Dell Wireless 1703 card. After reading dejavou42's post, I decided to play around with frequencies. So if anyone has this same issue on this same laptop, do the following:
1) Go to Network and Sharing Center
2) Change adapter settings
3) Right click on Wi-Fi adapter, select properties
4) Click on configure, then go to advanced tab
5) Select HT Mode, and change the value to HT Mode 20|40
6) Click OK, then you should be able to ping your router and any site
FYI, I tried everything out there. This was the only thing that worked for me.