Yes Stefano, I got IE
I just don't understand as the OP said squid was disabled, therefore IE should have no proxy set??
He therefore should not have had to manually set 'no proxy'.
Not logical Captain
Nope, but it could be some caching issue, a configuration error, another device on which the proxy hostname points which deliver the proxy.pac file etc...
Disabling proxy detection is always a good idea anyway. If you need a proxy, set it manually and you won't have bad surprises (especially when you're connecting remotely through a VPN)