See http://lists.wikimedia.org/pipermail/mediawiki-l/2013-April/040970.html
I remember that WMF had a similar problem, is there a solution apart from dropping the old jobs?
Version: 1.21.x
Severity: critical
URL: http://lists.wikimedia.org/pipermail/mediawiki-l/2013-April/040970.html
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=60719