[PC-BSD Testing] PC-BSD 9.1 update failed miserably (amd64, inside VirtualBox)

[Productnews]

I did an online upgrade from PC-BSD 9.1-RC3 to 9.1, and my whole kdm
environment is gone.
I run PC-BSD inside VirtualBox (it  does not run on the iron, see bug
http://www.freebsd.org/cgi/query-pr.cgi?pr=170677  amd64/170677 amd64
   FreeBSD 9.x does not boot if 2 hard disks are on system)

I started the Update Manager and selected the only available option, the
upgrade to 9.1.
After the download (some hours), I rebooted for the installation.
The installation started, and after some time, a message like "/ file
system full" appeared, and a button for reboot.
I rebooted, and software sets starting with akonadi  were being installed.
Eventually the login screen appeared. Wneh I logged in (KDE), all KDE
apps were gone: no konsole, no dolphin, ...
Only fluxbox works.

I should have ample disk space:
$ zpool list
NAME    SIZE  ALLOC   FREE    CAP  DEDUP  HEALTH  ALTROOT
tank0  26.8G  13.9G  12.9G    51%  1.00x  ONLINE  -

$ zfs list
NAME                        USED  AVAIL  REFER  MOUNTPOINT
tank0                      13.9G  12.4G   280M  legacy
tank0/usr                  13.3G  12.4G  12.3G  /usr
tank0/usr/home              375M  12.4G    32K  /usr/home
tank0/usr/home/hvf          375M  12.4G   375M  /usr/home/hvf
tank0/usr/ports             235M  12.4G   225M  /usr/ports
tank0/usr/ports/distfiles  6.04M  12.4G  6.04M  /usr/ports/distfiles
tank0/usr/ports/packages   4.42M  12.4G  4.42M  /usr/ports/packages
tank0/usr/src               352M  12.4G   352M  /usr/src
tank0/var                   337M  12.4G   209M  /var
tank0/var/crash            31.5K  12.4G  31.5K  /var/crash
tank0/var/db                127M  12.4G   105M  /var/db
tank0/var/db/pkg           21.9M  12.4G  21.9M  /var/db/pkg
tank0/var/empty              31K  12.4G    31K  /var/empty
tank0/var/log               370K  12.4G   370K  /var/log
tank0/var/mail               32K  12.4G    32K  /var/mail
tank0/var/run                99K  12.4G    99K  /var/run

Any suggestions beside doing a fresh install or downloading a VrtualBox
image?
thanks, Harald