Login failed for user (null)

Any users out there resolve this one. Thanks in advance!

Login failed for user '(null)'. Reason: Not associated with a trusted SQL Server connection.

Description:An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details:System.Data.OleDb.OleDbException: Login failed for user '(null)'. Reason: Not associated with a trusted SQL Server connection.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[OleDbException (0x80004005): Login failed for user '(null)'. Reason: Not associated with a trusted SQL Server connection.]
 System.Data.OleDb.OleDbConnectionInternal..ctor(OleDbConnectionString constr, OleDbConnection connection) +1054593
 System.Data.OleDb.OleDbConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningObject) +53
 System.Data.ProviderBase.DbConnectionFactory.CreateNonPooledConnection(DbConnection owningConnection, DbConnectionPoolGroup poolGroup) +27
 System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) +47
 System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) +105
 System.Data.OleDb.OleDbConnection.Open() +37
 System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset, DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) +121
 System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) +137
 System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, String srcTable) +83
 System.Web.UI.WebControls.SqlDataSourceView.ExecuteSelect(DataSourceSelectArguments arguments) +1770
 System.Web.UI.DataSourceView.Select(DataSourceSelectArguments arguments, DataSourceViewSelectCallback callback) +17
 System.Web.UI.WebControls.DataBoundControl.PerformSelect() +149
 System.Web.UI.WebControls.BaseDataBoundControl.DataBind() +70
 System.Web.UI.WebControls.GridView.DataBind() +4
 System.Web.UI.WebControls.BaseDataBoundControl.EnsureDataBound() +82
 System.Web.UI.WebControls.CompositeDataBoundControl.CreateChildControls() +69
 System.Web.UI.Control.EnsureChildControls() +87
 System.Web.UI.Control.PreRenderRecursiveInternal() +41
 System.Web.UI.Control.PreRenderRecursiveInternal() +161
 System.Web.UI.Control.PreRenderRecursiveInternal() +161
 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1360

Did you use Windows Authentication to connect the SQL instance? The error message indicates that the SQL instance doesn't 'know' the login. You can try to add the login to the SQL instance as following:

1. Open SQL Server Management Studio

2. Go to the instance, explore 'Security'->rigth click 'Login'->'New login...', just add the account that you used to connect