Log on screen disappear

The primary log on is client for micrsoft network(the property of client for
microsoft network had been type the domain name in the blank ,tick the check
box and choose reconnect all the network drive when start up)
and the pc log on a domain server,the logon screen should show on before i
see the desktop,but i never see it. i need to click logoff manually for the
domain logon.what's wrong