HELP! core dumps: install, mtree, et cetera all of the sudden after portmaster security/cyrus-sasl2

I ran into a very delicate and nasty situation.

On several boxes, FreeBSD 9.1-PRE and FreeBSD 10-CURRENT (build of
CURRENT sources from yesterday, r239295 Wed August 15 17:04:51 CEST 2012
amd64, I had to recompile all requirements of port Apache22, since after
the port update it core dumped.

On FreeBSD 9.1-PRE, with pkg(ng), things went well. Recompilation and
installation of all "portmaster -f apache-2.2" requirements went perfect.

On both FreeBSD 10-CURRENT boxes it ended up in a mess, all of a
sudden(!), while reinstalling port security/cyrus-sasl2, things started
to fail in a dramatik way!

On both FBSD 10 boxes, the installation of the port security/cyrus-sasl2
got corrupted by "install" and/or "mtree" dumping core and signalling
SIGNAL 11. Booting into multiuser mode is impossible, login core dumps
SIGNAL 11, many other daemons, too. The only way is to boot into single
user mode.

An installation failed due to pkg(ng) was missing libarchive.so via
portmaster or via core dumping install(1). By installing on one box, my
home box, port security/cyrus-sasl2 manually, luckily install(1) and
mtree(1) didn't coredump and it worked - and this precedure rescued me.
But on my lab's development box, it doesn't work!

On this specific box, where this nasty problem also occured the same way
by simply recompiling everything for port www/apache22, including the
reinstallation of port security/cyrus-sasl2. Nearly every binary is
suddenly coredumping (as on the home box). login, vi, install, devfs,
syslogd, mtree, id, find ... a whole lot of binaries seem to be
compromised by something I do not see (libsasl2.so perhaps?).

I tried to help myself via copying /rescue/vi to /usr/bin/vi to have at
least a working vi. But in /rescue, I can not find install or mtree. I'm
not familiar with the sophisticated ways of /rescue. Where are
install(1) and mtree(1)?

Trying to reinstall security/cyrus-sasl2 from single-user fails due
install coredumps. pkg(ng) fails due to missing libpkg.so.5 and even
rejects being reinstalled. But /usr/local/lib/libpkg.so.0 is even there!
Disabling the use of pkg with commenting out WITH_PKGNG=yes in
/etc/make.conf leads to the above issues with mtree and install.
Disabling this pkgng tag leads to reinstallation of missing packages,
which are store in the pkgng sqlite format and not as ASCII anymore, but
then I get
/var/runld-elf.so.hints: No such file or directory
Error: shared library "iconv.3" does not exist.

But most of the libs have never been touch! So what is the loader
complaining about?

Well, I'm floating like a dead man in the water and I'm glad that one
box survided although suffering from the same symptomes.

I tried to find rescue images and a rescue DVD of a snap shot server,
but there is no way to crawl through the informations on the web pages
towards a snapshot. All folders end up in 2011 and highly outdated
(www.freebsd.org, I didn't look at mirrors since I thought the main
server carries the most recent stuff). This isn't funny. No lead, no
hint, even in the download section.

If someone has some hints how to recompile the sources with an emergency
booted disk, I highly appreciate some desater advice. Maybe the release
of FreeBSD-10-CURRENT sources I compiled do have accidentally a nasty
bug, so it would be nice to update the sources and have a complete
recompilation done.

Thanks in advance,

oh