My computer refuses to connect to external servers like Steam, Impulse or any...

[MadTVMania]

...torrent.? The only firewalls I have are AVG and Windows Firewall, both of which have worked perfectly in the past and have "exceptions" set up for all the programs I use. I connect through a router, but it's not wireless, and again has worked without any problems previously. This problem has persisted now for more than a month, obviously I've restarted my computer and re-installed Steam and other programs during that time. I believe this may be a virus, but AVG cannot connect to the Update Server, and none of the programs I try seem to find anything.