I am having a problem with QueueUserWorkItem. I thought there was a maximum
number of worker threads a threadpool had available, 25 per processor, or
something like that. However, when executing the following code, after about
125 or so Excel processes are running I get:

"An unhandled exception of type
'System.Runtime.InteropServices.COMException' occurred in Fiscal Year
End.exe"

Additional information: Server execution failed

When another thread starts to execute.  I would expect at most 50 concurrent
Excel threads on a P4 hyperthreading system. Is there something wrong in my
code that keeps the system from recognizing the maximum thread count?

Private ExcelPool As System.Threading.ThreadPool

<Some Code>

For Each AccountRow In ReportingDS.Tables("Ledger Accounts").Rows
   SummaryRows = AccountRow.GetChildRows("Account Summary")
   For Each SummaryRow In SummaryRows
       TargetRange = WS.Cells(CurrentRow, 1)
       TargetRange.Resize(1, _
            SummaryRow.ItemArray.GetLength(0)).Value = SummaryRow.ItemArray
       TargetRange = WS.Cells(CurrentRow, 1)
       WS.Hyperlinks.Add(TargetRange, SaveSubDirectoryString & _
            WS.Cells(CurrentRow, 1).Value & ".xls", , _
           "Click on account number to open account activity.", _
               WS.Cells(CurrentRow, 1).Value)
       CurrentRow += 1
   Next
   Dim StObj As New StateObj
   StObj.DataRowArg = AccountRow.GetChildRows("Account Detail")
   StObj.DataTableArg = ReportingDS.Tables("Ledger Detail").Clone
   StObj.SavePath = SaveSubDirectoryString & AccountRow(0) + ".xls"
   StObj.DSName = AccountRow(0)
   ExcelPool.QueueUserWorkItem(New System.Threading.WaitCallback _
       (AddressOf SaveExcelData), StObj)
Next

<More Code>

Private Sub SaveExcelData(ByVal StateObj As Object)
   Dim StObj As StateObj
   StObj = CType(StateObj, StateObj)
   Dim ThreadExcel As New Excel.Application
   Dim ThreadWorkbook As Excel.Workbook = ThreadExcel.Workbooks.Add
   While ThreadWorkbook.Worksheets.Count > 1
       ThreadWorkbook.Worksheets(ThreadWorkbook.Worksheets.Count).Delete()
   End While
   Dim ThreadWorksheet As Excel.Worksheet = ThreadWorkbook.Worksheets(1)
   Dim DR As DataRow
   Dim DC As DataColumn
   For Each DC In StObj.DataTableArg.Columns
       ThreadWorksheet.Cells(1, DC.Ordinal + 1) = DC.ColumnName
   Next
   ThreadWorksheet.Rows(1).Font.Bold = True
   ThreadWorksheet.Rows(1).Font.Underline =
Excel.XlUnderlineStyle.xlUnderlineStyleSingle
   Dim CurrentRow As Integer = 2
   Try
       For Each DR In StObj.DataRowArg
           For Each DC In StObj.DataTableArg.Columns
               ThreadWorksheet.Cells(CurrentRow, DC.Ordinal + 1).Value =
DR(DC.Ordinal)
           Next
           CurrentRow += 1
       Next
   Catch ex As Exception
       MsgBox(ex.Message, MsgBoxStyle.Critical, "Thread Excel")
       ThreadWorksheet = Nothing
       ThreadWorkbook = Nothing
       ThreadExcel.Quit()
       ThreadExcel = Nothing
   End Try
   ThreadWorkbook.SaveAs(StObj.SavePath)
   ThreadWorkbook.Close()
   ThreadExcel.Quit()
   ThreadExcel = Nothing
   StObj = Nothing
End Sub