Index: wp-admin/includes/ajax-actions.php
===================================================================
--- wp-admin/includes/ajax-actions.php	(revision 22953)
+++ wp-admin/includes/ajax-actions.php	(working copy)
@@ -1602,9 +1602,11 @@
 		$wp_filetype = wp_check_filetype_and_ext( $_FILES['async-upload']['tmp_name'], $_FILES['async-upload']['name'], false );
 		if ( ! wp_match_mime_types( 'image', $wp_filetype['type'] ) ) {
 			echo json_encode( array(
-				'success'  => false,
-				'message' => __( 'The uploaded file is not a valid image. Please try again.' ),
-				'filename' => $_FILES['async-upload']['name'],
+				'success' => false,
+				'data'    => array(
+					'message'  => __( 'The uploaded file is not a valid image. Please try again.' ),
+					'filename' => $_FILES['async-upload']['name'],
+				)
 			) );
 
 			wp_die();
@@ -1615,9 +1617,11 @@
 
 	if ( is_wp_error( $attachment_id ) ) {
 		echo json_encode( array(
-			'success'  => false,
-			'message'  => $attachment_id->get_error_message(),
-			'filename' => $_FILES['async-upload']['name'],
+			'success' => false,
+			'data'    => array(
+				'message'  => $attachment_id->get_error_message(),
+				'filename' => $_FILES['async-upload']['name'],
+			)
 		) );
 
 		wp_die();
Index: wp-includes/css/media-views.css
===================================================================
--- wp-includes/css/media-views.css	(revision 22953)
+++ wp-includes/css/media-views.css	(working copy)
@@ -790,7 +790,9 @@
 
 .media-uploader-status {
 	position: relative;
+	margin: 0 auto;
 	padding-bottom: 10px;
+	max-width: 400px;
 }
 
 .media-sidebar .media-uploader-status {
@@ -842,7 +844,6 @@
 }
 
 .upload-errors .upload-error {
-	max-width: 400px;
 	margin: 8px auto 0 auto;
 	padding: 8px;
 	border: 1px #c00 solid;
@@ -868,6 +869,7 @@
 	display: block;
 	padding-top: 8px;
 	color: #b44;
+	word-wrap: break-word;
 }
 
 .uploader-window {