Index: wp-includes/media.php
===================================================================
--- wp-includes/media.php	(revision 22801)
+++ wp-includes/media.php	(working copy)
@@ -1235,13 +1235,16 @@
  */
 function wp_prepare_attachment_for_js( $attachment ) {
 	if ( ! $attachment = get_post( $attachment ) )
-	   return;
+		return;
 
 	if ( 'attachment' != $attachment->post_type )
-	   return;
+		return;
 
 	$meta = wp_get_attachment_metadata( $attachment->ID );
-	list( $type, $subtype ) = explode( '/', $attachment->post_mime_type );
+	if ( false !== strpos( $attachment->post_mime_type, '/' ) )
+		list( $type, $subtype ) = explode( '/', $attachment->post_mime_type );
+	else
+		list( $type, $subtype ) = array( $attachment->post_mime_type, '' );
 
 	$attachment_url = wp_get_attachment_url( $attachment->ID );