The 17 branched compose the 64 bit tree is failing to build images and be installable. 
The 32bit side is working fine. 

See:
http://kojipkgs.fedoraproject.org/mash/branched-20120228/logs/pungify-x86_64.log
and
http://kojipkgs.fedoraproject.org/mash/branched-20120228/logs/pungify-i386.log
(for example)

Excerpt from the x86_64 log: 

populating output tree and building boot images
running x86.tmpl
mount: unknown filesystem type 'hfsplus'
Traceback (most recent call last):
  File "/usr/sbin/mkefiboot", line 105, in <module>
    mkmacboot(opt.bootdir, opt.outfile, opt.label, opt.icon)
  File "/usr/sbin/mkefiboot", line 35, in mkmacboot
    mkhfsimg(None, outfile, label=label, graft=graft)
  File "/usr/lib/python2.7/site-packages/pylorax/imgutils.py", line 292, in mkhfsimg
    mkfsargs=["-v", label], graft=graft)
  File "/usr/lib/python2.7/site-packages/pylorax/imgutils.py", line 272, in mkfsimage
    with Mount(loopdev, mountargs) as mnt:
  File "/usr/lib/python2.7/site-packages/pylorax/imgutils.py", line 190, in __enter__
    self.mnt = mount(self.dev, self.opts, self.mnt)
  File "/usr/lib/python2.7/site-packages/pylorax/imgutils.py", line 101, in mount
    check_call(mount + [dev, mnt])
  File "/usr/lib64/python2.7/subprocess.py", line 511, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['mount', '/dev/loop0', '/tmp/lorax.imgutils.rhw2c2']' returned non-zero exit status 32
template command error in x86.tmpl:
  runcmd mkefiboot --label=ANACONDA --apple --icon=/tmp/treebuild.20120228/output/work/x86_64/installroot/usr/share/pixmaps/bootloader/fedora.icns /tmp/treebuild.20120228/output/17/x86_64/os/EFI/BOOT /tmp/treebuild.20120228/output/17/x86_64/os/images/macboot.img
  NameError: global name 'CalledProcessError' is not defined
Traceback (most recent call last):
  File "/usr/bin/pungi", line 226, in <module>
    main()
  File "/usr/bin/pungi", line 126, in main
    mypungi.doBuildinstall()
  File "/usr/lib/python2.7/site-packages/pypungi/__init__.py", line 849, in doBuildinstall
    workdir=workdir, outputdir=outputdir)
  File "/usr/lib/python2.7/site-packages/pylorax/__init__.py", line 241, in run
    treebuilder.build()
  File "/usr/lib/python2.7/site-packages/pylorax/treebuilder.py", line 196, in build
    self._runner.run(templatefile, kernels=self.kernels)
  File "/usr/lib/python2.7/site-packages/pylorax/ltmpl.py", line 135, in run
    self._run(commands)
  File "/usr/lib/python2.7/site-packages/pylorax/ltmpl.py", line 154, in _run
    f(*args)
  File "/usr/lib/python2.7/site-packages/pylorax/ltmpl.py", line 377, in runcmd
    except CalledProcessError as e:
NameError: global name 'CalledProcessError' is not defined

This could be a pungi bug as well, but looks like it's failing in pylorax. 

Happy to provide more info...