If you are receiving following error:
TITLE: Connect to Server
Cannot connect to Database Server.
An error has occurred while establishing a connection to the server. When connecting to SQL Server 2005, this failure may be caused by the fact that under the default settings SQL Server does not allow remote connections. (provider: Named Pipes Provider, error: 40 – Could not open a connection to SQL Server) (Microsoft SQL Server, Error: 1326)
I suggest that you read previous article first as that describes how to fix the problem and has worked for many cases.
Now if SQL Server can be connected perfectly from local system but can not be connected from remote system, in that case firewall of the server where SQL Server is installed can be issue.
Follow instructions of this article to fix the issue.
Go to control panel >> Firewall Settings >> Add SQL Server’s Port to Exception List.
Now try to connect to SQL Server again. It will allow you to connect to server successfully.
Reference : Pinal Dave (http://blog.SQLAuthority.com)