I am running a web service on my local machine (using standard VS.NET test
pages) that is attempting to access a SQL database on a network server.  C#
code looks something like this:

[WebMethod]
public string GetSomething()
{
 SqlConnection con = new SqlConnection();
 con.ConnectionString =
ConfigurationSettings.AppSettings["connectstring"].ToString();
 con.Open();
 ...
}

The problem is that the Open() statement always yields a "SQL Server does
not exist or access denied" message.  The same code works fine when run from
a WinForms app, so I know that my connection string is good.  Is this a
permissions issue or am I missing a setting somewhere?

Thanks in advance.
David