Alright, in that case it's definitely not your browser. I need to go out now so I will just leave a few things to try here:
First of all, if you haven't already, reboot the PC, restart the router and the modem.
Second, try pinging Google's IP. See if your results are any different.
If they are not different, trying pinging the default gateway. See if the results are any better.
If the results of pinging the gateway are the same as pinging outside, it means the issue is with your connection to the router. Otherwise, try bypassing the router and connecting straight to the modem (if they are separate) and try the same thing. If you get better results connected straight to the modem, that means the issue is on your ISP's end, so call them. Otherwise, it's got to do with the connection between the PC/Router and the modem.
Based on what results you get hopefully someone else will be able to help you, otherwise I will take a look when I get home