Index: wp-admin/upload.php
===================================================================
--- wp-admin/upload.php	(revision 2597)
+++ wp-admin/upload.php	(working copy)
@@ -83,7 +83,7 @@
 	$imgalt = basename( (isset($_POST['imgalt'])) ? $_POST['imgalt'] : '' );
 
 	$img1_name = (strlen($imgalt)) ? $imgalt : basename( $_FILES['img1']['name'] );
-	$img1_name = preg_replace('/[^a-z0-9_.]/i', '', $img1_name); 
+	$img1_name = preg_replace('/[^a-z0-9_.-]/i', '', $img1_name); 
 	$img1_size = $_POST['img1_size'] ? intval($_POST['img1_size']) : intval($_FILES['img1']['size']);
 
 	$img1_type = (strlen($imgalt)) ? $_POST['img1_type'] : $_FILES['img1']['type'];
@@ -227,4 +227,4 @@
 break;
 }
 include('admin-footer.php');
-?>
\ No newline at end of file
+?>