The OfficeScan server was unable to reach the update source

Another problem encountered today :-(
"The OfficeScan server was unable to reach the update source. Please verify that the update source is correct."
After a little investigation the problem was easier solved. The firewall blocked the machine HTTP navigation (fast to be discovered: explorer wasn't working :-)
After unblocking the port 80 from the firewall the OfficeScan update engine resume working.