I did exactly this - to the extent of C/P the lines above - and it worked without a problem. The only difference to the first try was the run under script. Btw the vm is zfs-based, so pkg and pkgsrc are zfs datasets (cleaning /usr/pkg was 'zfs destroy' and 'zfs create').
Go figure...
Chavdar
(well, there was one more difference - with the first try I just in case copied the newly created /usr/pkg/etc/mk.conf to /etc, which did not make difference. I didn't remove this file when I ran the second trial, I wonder if this may have scewed the result).