I'm using AVG Internet Security 2011. I tried to deactivate its Online Shield and all other "extra" features, and check the Firewall state as you mentioned. It didn't work until I disabled ALL of the extra features, and apparently the problem is solved when I leave only the Antivirus, Antispyware and the Firewall, that is, the basic properties. I'll try other filehosts to see if this works for them too. Thanks for your help!