Index: wp-admin/includes/ajax-actions.php
===================================================================
--- wp-admin/includes/ajax-actions.php	(revision 22925)
+++ wp-admin/includes/ajax-actions.php	(working copy)
@@ -1899,6 +1899,10 @@
 	if ( 'attachment' != $post['post_type'] )
 		wp_send_json_error();
 
+	// Handle the description field automatically, if a plugin adds it back.
+	if ( isset( $attachment_data['post_content'] ) )
+		$post['post_content'] = $attachment_data['post_content'];
+
 	$post = apply_filters( 'attachment_fields_to_save', $post, $attachment_data );
 
 	if ( isset( $post['errors'] ) ) {
Index: wp-admin/includes/media.php
===================================================================
--- wp-admin/includes/media.php	(revision 22925)
+++ wp-admin/includes/media.php	(working copy)
@@ -1325,7 +1325,7 @@
 	$form_fields = apply_filters( 'attachment_fields_to_edit', $form_fields, $post );
 
 	unset( $form_fields['image-size'], $form_fields['align'], $form_fields['image_alt'],
-		$form_fields['post_title'], $form_fields['post_excerpt'], $form_fields['post_content'],
+		$form_fields['post_title'], $form_fields['post_excerpt'],
 		$form_fields['url'], $form_fields['menu_order'], $form_fields['image_url'] );
 
 	$media_meta = apply_filters( 'media_meta', '', $post );