Problem disabling Network Proxy

[bar tomas]

Hi,

I'm using Ubuntu and at work I have set a proxy configuration because
there is a firewall.
But as I am at home now, I have disabled the proxy by going to the
menu System/Preferences/Network Proxy and unchecking the proxy option
so that  Direct Internet Connection is selected.
However when I have tried using apt-get to install a package I get an error:
'Could not resolve poe' (poe is the name of my proxy server at work)

Is disabling the proxy through System/Preferences/Network Proxy not
enough? Do I have to do any additional configuration?

Many thanks.