This condition arises if a process(es) monopolizes the system in terms of CPU usage or table blocking. Possibility also running out of transaction log space.

If EM times out on you, you have to try a thinner client:

isql

osql

Query Analyzer

If still locked out, send a "netsend" message to everybody, to see if someone is connected. If you find a connected person, walk over there, or give instructions on the phone.

When connected, identify the runaway process, consult with the owner, either let it run to conclusion or kill it.

As a final option, if unable to connect, reboot the server.