Lost connection, cannot activate eth0
I am running fedora vm under XP host and using NAT connection to the Internet. It usually works fine, but some time the connection is just lost. I went menu System->Admin->Network and see the interface eth0, but I cannot activate or deactivate. The status is inactive. (when the connect works, the status is active). so I try "ifdown eth0" and "ifup eth0" command, and got
"Error: Connection activation failed: Device not managed by NetowrkManger
The menu System->Admin->Network device control show no interface.
I am not sure what happened.