[otrs] Ticket linking fails

Hi, we run otrs 1.2.4 on SuSE with postgres. So far so good. Today I receive error messages when trying to link Tickets. The original Ticket is A, I successfully linked B to it, and now I want to add an additional link to C. There have been similar problems in the past, which I circumvented by changing the order of the link, but this does not help this time. The error in the system reads like: ERROR: duplicate key violates unique constraint "ticket_link_ticket_id_maste_key", SQL: 'INSERT INTO ticket_link (ticket_id_master, ticket_id_slave) VALUES (1269, 1270) ' Could anybody explain me please why there is a unique constraint on the master_key (Typo? ...maste_key ). Searching the mail archives gave no match so far. Regards Gerold