Login failed for user ''. The user is not associated with a trusted SQL Server connection.

If you see this error in your log files:

<LogEntry>
<LogType>Error</LogType>
<Timestamp>2015-06-01 01:12:14-05:00</Timestamp>
<UserID>00000000-0000-0000-0000-000000000000</UserID>
<AuthorizationUser><![CDATA[UserName]]></AuthorizationUser>
<Message><![CDATA[An error occurred while accessing the folder with ID, ',' and provider name, '.']]></Message>
<Exception>
<![CDATA[System.Data.SqlClient.SqlException: Login failed for user ''. The user is not associated with a trusted SQL Server connection.
at System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject)
at System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection)
at System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory)
at System.Data.SqlClient.SqlConnection.Open()
at Passageways.Portal.Util.Database.CreateConnection()
at Passageways.Portal.Util.Database.ExecuteReader(CommandType commandType, String commandText, IEnumerable`1 commandParameters)
at Passageways.Portal.Web.Documents.NetworkDocumentsProvider.GetChildren(Object folderID, EventHandler`1 errorHandler)
at Passageways.Portal.Web.Server.DocumentRepositoryService.GetRootFolders(EventHandler`1 errorHandler)
at Passageways.Portal.Web.Runtime.Documents.Document.ProcessFolder(HttpContext context, String folderID, String providerName)
]]></Exception>
</LogEntry>

The culprit is the SQL server.  The SQL Server has lost connection to the domain that the web server is a part of, and so the Trusted Connection between the domain and the server cannot be established.

Reconnect the server to the domain to solve the problem.