UTC ERROR: could not obtain lock on row in relation "ir_cron"

[D Verhelst]

when launching openerp7 (up until latest nightly) i get a multi-trheaded cron issue:

2013-03-05 06:37:31 UTC STATEMENT: SELECT *
                                    FROM ir_cron
                                    WHERE id=2
                                    FOR UPDATE NOWAIT
2013-03-05 06:37:31 UTC ERROR: could not obtain lock on row in relation "ir_cron"

this appears to be because cron: and cron:0 try to run the same command?
solved by tuning down config :

max_cron_threads = 1

seems to work fine, for now