There is a client out there that is handling the handshake wrong by replying with 0.6 on a 0.4 connection. Maybe Phex is a little strict here but not wrong, the connection will just be dropped.

Check these links for further information:
http://groups.yahoo.com/group/the_gdf/message/4108
http://groups.yahoo.com/group/the_gdf/message/4136

Gregor