SQL Server problem

[Vibyera]

I get following error message while attempting to connect to a MS SQL Server:
A connection was successfully established with the server, but then an error occurred during the pre-login handshake. (provider: TCP Provider, error: 0 – The specified network name is no longer available.) (Microsoft SQL Server, Error: 64)
what causes the problem?

[zmbd]

what kind of network are you on?
I've seen this when the connection is on a dynamic ip-address.
I've also seen this when the firewall dropped the connection.