Admin Server Connection Error

i believe there should be some network issues. Or server not properly started.

with fm10, the server admin tool is a separate service/daemon from the fm server itself, so the admin console may go nuts while the server is OK. restarting the whole server or at least the admin service should fix it. on my machine it happens when you leave the admin console open for a while wihtout doing anything.
Can you still open dbs without any pb?

Yes, the databases open just fine.  I have restarted the whole server twice, but still get the same error. This is FM9.  I have FM 10, but not ready to install it yet.

I don't have any fm9 server running here...
can you test locally on server if ok?
any change on your firewall or server's one which would block port 16000?
what is your server? win or osx?

I tried on the server and on my desktop.  I have a windows 2003 server.
I am running an antivirus system, I wonder if it would block ports?

well... depends, some AV are now having features of a firewall before, so the limit is not obvious.
but the windows firewall can block these ports, even when talking to yourself!, so put it off if you use it.
you need port 16000 for the tomcat server (embedded in fm server for admin app.), and 50003 & 50006 for remote admin comm in between the admin tool and fm server itself.