I have solved the error, after some days trying solutions, I have found an error in my ZeroShell setup. I had well configured DHCP then the clients get well internet connection, but the DNS server in ZeroShell had bad forwarders. I have setup the correct forwardes and the “Packet Manager” get connection with “http://updates.zeroshell.org”
I don’t use the DNS server on ZeroShell, but I think is necesary get correct setup.