This might be a bit "basic" to start...but
download CCleaner and run it. Clear everything. (Unless you have stuff in your recycle bin you want to keep.) Also just for good measure, clear your registry with it too.
(Can be found right under "Cleaner)
Also, it looks like you're on Vista at least, so try this:
Go in to your Start Menu, and search "Network and Sharing Center." On the left side, click "Manage Networks." In there, delete the network you're currently on, and reconnect to it. (If you have a password and you set it to automatically connect, you will have to retype the password.)
Have you tried any other browsers, too? Try that before attempting these fixes, because it "could" save you some time.
Hope this works!