Fatal Execution Engine Error was detected.

Using VS 2010 with AutoCAD 2013 or 2014.

I am getting Fatal Execution Engine Error was detected.

The runtime has encountered a fatal error. The address of the error was at 0xe79d9f1a, on thread 0x1080. The error code is 0xc0000005. This error may be a bug in the CLR or in the unsafe or non-verifiable portions of user code. Common sources of this bug include user marshaling errors for COM-interop or PInvoke, which may corrupt the stack.

It is in the statement

DocumentExtension.CloseAndSave(acDocMgr.MdiActiveDocument, strFileName)

How do I begin to trouble shoot this?

Thank you,

I am using the following code in a loop.

Public Class MyCommands
       <CommandMethod("OSCLoop", CommandFlags.Session)> _
       Public Sub OSCLoop() ' This method can have any name
           ' Put your command code here
           Dim y As Integer
           Dim lines() As String = IO.File.ReadAllLines("C:\VBdwgFilelist.txt")
           Dim strFileName As String
           Dim lineArray As New ArrayList()
           Dim acDocMgr As DocumentCollection = Application.DocumentManager
           Dim acDoc As Document = Application.DocumentManager.MdiActiveDocument
           Dim obj As Object = Application.GetSystemVariable("DWGTITLED")
           y = 0
           For x As Integer = 0 To lines.GetUpperBound(0)
               'If TextBox1.Text = String.Empty Then
               If lines(x) <> String.Empty Then
                   lineArray.Add(lines(y))
                   y = y + 1
               End If
           Next
           'MsgBox("Show each line")
           For x = 0 To lineArray.Count - 1
               'MsgBox(lineArray.Item(x))
               'Open the drawing 
               strFileName = lineArray.Item(x)
               MsgBox(strFileName)
               If (File.Exists(strFileName)) Then
                   DocumentCollectionExtension.Open(acDocMgr, strFileName, False)
                   'START SAVE & CLOSE
                   'DocumentExtension.CloseAndDiscard(acDocMgr.MdiActiveDocument)
                   DocumentExtension.CloseAndSave(acDocMgr.MdiActiveDocument, strFileName)
                   MsgBox("Drawing Saved")
               Else
                   acDocMgr.MdiActiveDocument.Editor.WriteMessage("File " & strFileName & " does not exist.")

               End If
           Next
       End Sub
   End Class