Index: includes/file.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/file.inc,v
retrieving revision 1.174
diff -u -r1.174 file.inc
--- includes/file.inc	10 Jul 2009 04:08:20 -0000	1.174
+++ includes/file.inc	12 Jul 2009 06:31:42 -0000
@@ -1147,7 +1147,7 @@
 
   $info = image_get_info($file->filepath);
   if (!$info || empty($info['extension'])) {
-    $errors[] = t('Only JPEG, PNG and GIF images are allowed.');
+    $errors[] = t('The file is not a known image format.');
   }
 
   return $errors;