I was trying to try out the tutorials. But when I want to use the Business Object Mapper, the following errors appears:

SqlException
 Invalid object name 'DTEprojects'.
Invalid object name 'DTEproject_computer_tie'.

Source     : .Net SqlClient Data Provider

Stack Trace:
   at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection)
   at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection)
   at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj)
   at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)
   at System.Data.SqlClient.SqlDataReader.ConsumeMetaData()
   at System.Data.SqlClient.SqlDataReader.get_MetaData()
   at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString)
   at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async)
   at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result)
   at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)
   at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)
   at System.Data.SqlClient.SqlCommand.ExecuteDbDataReader(CommandBehavior behavior)
   at System.Data.Common.DbCommand.System.Data.IDbCommand.ExecuteReader(CommandBehavior behavior)
   at System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset, DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior)
   at System.Data.Common.DbDataAdapter.Fill(DataTable[] dataTables, Int32 startRecord, Int32 maxRecords, IDbCommand command, CommandBehavior behavior)
   at System.Data.Common.DbDataAdapter.Fill(DataTable dataTable)
   at MicroFour.StrataFrame.Data.DbDataSourceItem.GetDataTable(DbCommand Command, OnChangeEventHandler CallBack)
   at MicroFour.StrataFrame.Data.SqlDataSourceItem.GetDataTable(DbCommand Command, OnChangeEventHandler CallBack)
   at MicroFour.StrataFrame.Data.DataLayer.GetDataTable(DbCommand Command, Boolean RegisterNotification)
   at MicroFour.StrataFrame.Business.BusinessLayer.FillDataTable(DbCommand CommandToExecute)
   at MicroFour.StrataFrame.AddIns.DTEprojectsBO.FillProjects(String[] ProjectPaths)
   at MicroFour.StrataFrame.AddIns.PartialClassBuilderDialog.BuildProjectNode(PartialClassBuilderVSProject Prj)

Anyone can help?

Looks like your database connection for the StrataFrame design-time database is incorrect, or the StrataFrame design-time database in unavailable.  You can check your connection from within Visual Studio by opening the StrataFrame menu and choosing the "Database Connection" option.  In there, you can edit the connection and make sure it's pointing to the right place.