Only minimal images are created for x86_64 on 2012.08.22 . Link: http://autobuilder.yoctoproject.org/pub/nightly/20120822-1/machines/qemu/qemux86-64/
This would have been due to a build issue. This wouldn't be an Autobuilder bug.
As Beth stated, it was a build failure, that was the pango and RPM failures due to rpath issue which was fixed.
Setting to verified