My current code ran in VS2003 on a XPpro machine. I transferred it to a Vista machine and had to purchase VS2005 (VS2003 not supported). I made the necessary changes and the code ran. I made additions to the code over several weks and the code still compiiled successfully . I did not run the code a gain for about a month and then the code would not compile on the Vista machine so I installed VS2005 on an XPpro PC and ran the same code, which failed on Vista and it compiled and runs fine. Both PCs have Ofiice 2003 Pro on them and no other versions of Excel or office. It as if one of the MS regular Vista updates made a change causing the code not to compile. My code is in Visual Basic These are the first lines of the code Imports System.IO Imports System.IO.StreamReader Imports System Imports System.Threading Imports System.text.regularexpressions Imports System.Text Imports System.Globalization Imports System.Collections Imports Microsoft.Office.interop.excel Imports Excel = Microsoft.Office.Interop.Excel Imports System.Reflection Imports System.Runtime.InteropServices The lines following this are Windows Form Designer Generated code (about 2000 of them ) Total program is about 9000 lines Dim ExcelScheduler As New Excel.Application Dim ExcelWB As Excel.Workbook = ExcelScheduler.Workbooks.Open("C:\ExactaRecords\Scheduler.xls") Dim ScheduleSheet1 As Excel.Worksheet = ExcelWB.Sheets(1) Dim ScheduleSheet2 As Excel.Worksheet = ExcelWB.Sheets(2) Dim ScheduleSheet3 As Excel.Worksheet = ExcelWB.Sheets(3) ScheduleSheet1 = ExcelWB.Worksheets(1) ScheduleSheet2 = ExcelWB.Worksheets(2) ScheduleSheet3 = ExcelWB.Worksheets(3) This is the error message: System.InvalidCastException occurred Message="Unable to cast COM object of type 'Microsoft.Office.Interop.Excel.ApplicationClass' to interface type 'Microsoft.Office.Interop.Excel._Application'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{000208D5-0000-0000-C000-000000000046}' failed due to the following error: Library not registered. (Exception from HRESULT: 0x8002801D (TYPE_E_LIBNOTREGISTERED))." Source="Microsoft.Office.Interop.Excel" StackTrace: at Microsoft.Office.Interop.Excel.ApplicationClass.get_Workbooks() at ShowTimeScheduler.ShowTimeDirector..ctor() in C:\ShowTimeScheduler\Backup\ShowTimeDirector.vb:line 2222 Error occurs at the line : Dim ExcelWB As Excel.Workbook = ExcelScheduler.Workbooks.Open("C:\ExactaRecords\Scheduler.xls") I did try removing all references to 11.0 and tried earlier interops . I also cleaned the registry of all references to office and reinstalled office 2003 Pro and VS 2005 to no effect. I have also downloaded and reinstalled all the office PIAs Does any one have any ideas how to fix this problem? Thanks
