|The best way to eliminate the Hosts file from the equation is this:|
From Computer go to to your system drive (usually C). Follow this path:
Windows > System32 > drivers > etc
In the final folder (etc) see if you can see a file with just plain Hosts as its name. If you find this, rename it to xHosts which will disable it. Restart the system and see if your issue is resolved. If not go back and rename xHosts back to Hosts as it is not the culprit. If it does resolve the problem we can take it further.
The proxy settings in IE are unlikely to help as you have issues with Firefox. If you want to check though, go to:
IE > Tools > Internet Options > Connections tab > Lan settings button.
Make sure there is no check mark under Proxy server.
Always pop back and let us know the outcome - thanks