Only internet explorer is allowing me to access webpages, and windows live messenger, and i'm pretty sure my background apps (antivir, utorrent, etc) are all working online too, but Chrome and FF3 aren't able to open any webpages.
Make sure that your Windows firewall isn't blocking those applications. Even if you added them to the exemption list before, that firewall likes to randomly block stuff again.
Anway I think I might be able to help you with the problem. For Firefox.
Go Tools> Options> Advanced> Network tab> Settings and change the proxy settings to "Auto detect proxy settings for this network" OR "Manual proxy configuration" and put in your HTTP Proxy and Port number if you have them. Also tick "Use this proxy server for all protocols" if you use Manual proxy configuration cos I had some problems which were fixed by ticking the box.