Parameter is not valid - "pictureBox.Show()"

Question

I'm making a TIFF viewer with a picture box and buttons for going trought the pages of multi page files.

 

When I open a file for the first time, all works great, then I close it. But when I open a new file, after closing the previous one, I get an error saying "Parameter is not valid" at the line "pbtiff.Show()".

 

This is my code for opening the file:

private void openToolStripMenuItem_Click(object sender, EventArgs e)
{
   pbtiff.Hide();
   OpenFileDialog dialogo = new OpenFileDialog();
   dialogo.Title = "Search files";
   dialogo.InitialDirectory = @"E:\";
   dialogo.Filter = "PDF Files(.pdf)|*.pdf|Image Files (.bmp,.jpg,.png,.tiff,.tif) |*.bmp;*.jpg;*.png;*tiff;*tif";
   DialogResult answer = dialogo.ShowDialog();
   if (answer == DialogResult.OK)
   {
      string fullPath = dialogo.FileName;
      openFile = fullPath;
      using (var fileStream = new FileStream(ficheiroaberto, FileMode.Open))
      {
         type = Path.GetExtension(caminhoCompleto);
         if (type == ".tif" || type == ".tiff")
         {
            up.Visible = true;
            up.Enabled = false;
            down.Visible = true;
            pbtiff.Show(); -> the error is here, when I open the file for the 2nd time
            if (pbtiff.Image != null)
            {
               pbtiff.Image.Dispose();
            }
            pbtiff.Image = System.Drawing.Image.FromStream(fileStream);
            SplitTiffFinal(fileStream);
            filestiff = GetFilesFinal();
            up.Visible = true;
            up.Enabled = false;
            down.Visible = true;
         }
      }
   }
}

Can you help me figure out what is the probem, if it works the first time?