Index: wp-includes/pluggable.php
===================================================================
--- wp-includes/pluggable.php	(revision 19601)
+++ wp-includes/pluggable.php	(working copy)
@@ -1629,7 +1629,7 @@
 	}
 
 	if ( !empty($email) )
-		$email_hash = md5( strtolower( $email ) );
+		$email_hash = md5( strtolower( trim( $email ) ) );
 
 	if ( is_ssl() ) {
 		$host = 'https://secure.gravatar.com';