This is probably not a Firefox issue.

The most likely scenario is that you caught some malware that ran a proxy on your PC. Now that AVG has cleaned the malware, FF can't find the proxy it's been using. Your PC is basically saying, "what? No proxy here, get lost," If you fire up Internet Exploder, I bet you'll see the same result.

If the "evil" proxy setting was set in Firefox, you can reset it through options/advanced/network/settings. Change it to either "no proxy" or to "system proxy settings."

If Firefox already uses the system proxy, you'll need to modify the registry. Here's a decent start:

http://support.microsoft.com/kb/819961

You can find the connection settings in Tools > Options > Advanced : Network : Connection If you do not need to use a proxy to connect to internet then select "No Proxy" if the default "Use the system proxy settings" setting doesn't work.

See "Firefox connection settings":

• https://support.mozilla.com/kb/Firefox+cannot+load+websites+but+other+programs+can

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the extensions is causing the problem (switch to the DEFAULT theme: Firefox (Tools) > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.
• https://support.mozilla.com/kb/Safe+Mode

• https://support.mozilla.com/kb/Troubleshooting+extensions+and+themes