I have the same problem still version 7.400, i have activate the proxy server with antivirus scanner, i become the message Content block "failed to get scanner ..." when i deactivate the antivirus engine then everything all ok. But the ftp proxy with antivirus scanner is ok.
Whats that[:S]
P.S. Only the microsoft domain is ok when i surf via httpproxy and antivirus scanner, the other domain not.