Index: includes/theme.inc
===================================================================
--- includes/theme.inc	(revision 51)
+++ includes/theme.inc	(working copy)
@@ -1167,6 +1167,10 @@
  *   A string containing the image tag.
  */
 function theme_image($path, $alt = '', $title = '', $attributes = NULL, $getsize = TRUE) {
+  if (menu_path_is_external($path)) {
+    $getsize = FALSE;
+  }
+
   if (!$getsize || (is_file($path) && (list($width, $height, $type, $image_attributes) = @getimagesize($path)))) {
     $attributes = drupal_attributes($attributes);
     $url = (url($path) == $path) ? $path : (base_path() . $path);