It looks like there are currently different versions on CentOS 6.3 for the upstart RPM between i386 and x86_64:
http://mirror.centos.org/centos-6/6.3/os/i386/Packages/upstart-0.6.5-10.el6.... http://mirror.centos.org/centos-6/6.3/os/x86_64/Packages/upstart-0.6.5-12.el...
I'm not seeing any trouble as a result of this, but wanted to call it out. The current i386 RPM seems to be what CentOS 6.2 had. The upstream announcement http://rhn.redhat.com/errata/RHBA-2012-0863.html , from 2012-06-20, is for the upgrade from upstart-0.6.5-10.el6 to upstart-0.6.5-12 .
Thanks, Greg