BUG: Self looping edges are not unique

I'v tried to create several self pointing edges for ex: INSERT INTO `test_graph`.`edge` (`latch`, `origid`, `destid`, `weight`, `seq`, `linkid`) VALUES (NULL, '1', '1', NULL, NULL, NULL);

Running the same query leads to creating a doublicate record Unique Error doesn't fires

using: 5.0.87-d10-ourdelta-sail66 on ubuntu 9.10

PS. Also self looping edges become undeletable try: DELETE FROM `test_graph`.`edge` WHERE origid=1;

P.S. It doesn't happens every time. It seems that it happens under some strange conditions, I'll will try to analyse but I have no additional information