A generic error occurred in GDI+ error

I'm having a problem with running a report from a workflow using the TemplateReport activity. All of it works until I try to load an image from either disk or a url. 

I need to dynamically select what image appears in the report, so selecting an image at design time is out.

I have had the workflow downloading an image and putting it into a datatable in a dataset and providing that to the template report. 

I have also tried having the report itself load an image using script.

On my development VM both approaches work perfectly, but on the production server I keep getting the error 'A generic error occurred in GDI+'

Here's a simplified version of the report script:

public void Detail1_Format()

 

{

 

  string pictureUrl ="http://upload.wikimedia.org/wikipedia/commons/thumb/5/55/Potok_pod_jezerom_1.jpg/220px-Potok_pod_jezerom_1.jpg";

 

  //Setting up the image to retrieve webrequest

 

  System.Drawing.Image pinImage = null;

 

  System.Net.WebRequest req = System.Net.WebRequest.Create( pictureUrl );

 

  using( System.Net.WebResponse response = req.GetResponse() )

 

  using( System.IO.Stream stream = response.GetResponseStream() )

 

  {

 

     pinImage = System.Drawing.Image.FromStream( stream );

 

  }

 

  Picture PictureProperty = rpt.Sections["Detail1"].Controls["Picture1"] as Picture;

 

  PictureProperty.HyperLink = pictureUrl;  

 

  PictureProperty.DataField = pictureUrl;

 

  PictureProperty.Image = pinImage;

 

}

Has anyone seen this? Is there a work around?

Thanks,

Luke.