Which OS are you running on the PC?
When connected up via the router, open up a command prompt/terminal;
ping 209.85.171.100
ping 74.125.45.100
if you get valid replies, then you have Internet connectivity, in the same command prompt/terminal window, try;
ping google.com
if that DOESN'T give you a similar response then you possibly have a DNS issue. Change your PC's DNS settings to (OpenDNS - known to be working atm);
208.67.222.222
208.67.220.220
Repeat above ping tests.