Application Error

[bergerkiller]

It's hard to tell what the problem is, but the OS like to set lots of rules before you can access files.

What if you delete the file before copying?:

If System.IO.File.Exists(sfd.FileName) Then
    SetAttr(sfd.FileName, FileAttribute.Normal)
    IO.File.Delete(sfd.FileName)
End If
IO.File.Copy("bob.txt", sfd.FileName, True)

Ow, and you could try it with using a full path instead of a relative path:

            Dim sourcefile As String = Application.StartupPath & "\bob.txt"
            If IO.File.Exists(sourcefile) Then
                Dim sfd As New SaveFileDialog
                If sfd.ShowDialog = Windows.Forms.DialogResult.OK Then
                    Dim destfile As String = sfd.FileName
                    If System.IO.File.Exists(destfile) Then
                        SetAttr(destfile, FileAttribute.Normal)
                        System.IO.File.Delete(destfile)
                    End If
                    IO.File.Copy(sourcefile, destfile)
                End If
            End If

But, since the error is about the "bob.txt" file (saw it too late), I might have a clue of what is going on. In case you wrote the file "bob.txt" in your program, do not forget to close your writer:

            Dim writer As New System.IO.StreamWriter("bob.txt", True)
            writer.WriteLine("line")
            writer.Close() '<- very important

If you used the System.IO.File.WriteAllText it could be the system forgot to close the writer.

Just in case, are you sure the file is not used by your program or was used in the past during the runtime of your program?