--- imagefield/imagefield.module	2009-03-20 08:37:36.000000000 +0200
+++ /usr/local/share/drupal/modules/imagefield/imagefield.module	2009-03-28 17:07:47.000000000 +0200
@@ -259,7 +259,9 @@ function theme_imagefield_image($file, $
   if (!empty($alt)) {
     $attributes['alt'] = $alt;
   }
-  $url = file_create_url($file['filepath']) . '?' . $file['timestamp'];
+
+  $url = file_create_url($file['filepath']) . ( variable_get('file_downloads', FILE_DOWNLOADS_PUBLIC) == FILE_DOWNLOADS_PRIVATE ? '&' : '?' ) .
+	$file['timestamp'];
   $attributes['src'] = $url;
   $attributes = drupal_attributes($attributes);
   return '<img '. $attributes .' />';