Example:

 asteria /usr/lib/portage # emerge -NDvp world

 These are the packages that would be merged, in order:

 Calculating world dependencies... done!
 [ebuild   R   ] x11-base/xorg-server-1.1.1-r1  USE="dri nptl sdl xorg xprint -3dfx -aiglx% -debug -dmx -ipv6 -kdrive -minimal" INPUT_DEVICES="keyboard mouse -acecad -aiptek -calcomp -citron -digitaledge -dmc -dynapro -elo2300 -elographics -evdev -fpit -hyperpen -jamstudio -joystick -magellan -microtouch -mutouch -palmax -penmount -spaceorb -summa -synaptics -tek4957 -ur98 -vmmouse -void -wacom" VIDEO_CARDS="i810 -apm -ark -chips -cirrus -cyrix -dummy -epson -fbdev -fglrx -glint -i128 -i740 (-impact) -imstt -mach64 -mga -neomagic (-newport) -nsc -nv -nvidia -r128 -radeon -rendition -s3 -s3virge -savage -siliconmotion -sis -sisusb (-sunbw2) (-suncg14) (-suncg3) (-suncg6) (-sunffb) (-sunleo) (-suntcx) -tdfx -tga -trident -tseng -v4l -vesa -vga -via -vmware -voodoo" 0 kB 
 [ebuild     U ] net-im/sim-0.9.4.1 [0.9.4] USE="spell ssl -debug -kde" 3,253 kB 
 [ebuild   R   ] media-sound/fluidsynth-1.0.7  USE="alsa jack lash -static (-sse%*)" 0 kB 
 [ebuild     U ] net-misc/openssh-4.4_p1-r5 [4.4_p1-r4] USE="X kerberos ldap pam tcpd -X509 -chroot -hpn -libedit (-selinux) -skey -smartcard -static" 0 kB 
 [ebuild   R   ] net-im/gaim-1.5.0  USE="eds gnutls nls perl spell tcl tk -cjk -debug -krb4% -nas -silc" 0 kB 
 [ebuild   R   ] media-libs/xine-lib-1.1.2-r2  USE="X a52 alsa asf dts dvd esd fbcon flac gnome imagemagick mng mp3%* nls opengl samba sdl theora vcd vidix vorbis win32codecs xv xvmc -aac -aalib (-altivec) -arts -debug -directfb -dxr3 -ipv6 -libcaca -modplug -oss -speex -v4l -xinerama (-mad%*)" VIDEO_CARDS="i810 -nvidia -via" 22 kB 

 Total size of downloads: 3,276 kB

 asteria /usr/lib/portage # emerge -NDv world
 Calculating world dependencies... done!

 >>> Emerging (1 of 6) x11-base/xorg-server-1.1.1-r1 to /
 asteria /usr/lib/portage # 

/var/log/emerge.log shows the following in result:
 1161777789: Started emerge on: Oct 25, 2006 14:03:09
 1161777789:  *** emerge --newuse --deep --verbose world
 1161777802:  >>> emerge (1 of 6) x11-base/xorg-server-1.1.1-r1 to /
 1161777802:  === (1 of 6) Cleaning (x11-base/xorg-server-1.1.1-r1::/usr/portage/x11-base/xorg-server/xorg-server-1.1.1-r1.ebuild)
 1161777802:  *** terminating.

The only cure I found so far is to manually replace the contents of /usr/lib/portage/bin/ and /usr/lib/portage/pym/ directories with the respective ones from /usr/portage/distfiles/portage-2.1.2_pre3.tar.bz2.
But you all will agree that this can't be called a real solution.

Usually, my emerge --info looks like this:

 asteria /usr/lib/portage # emerge --info
 Portage 2.1.2_pre3 (default-linux/x86/2006.1/desktop, gcc-4.1.1, glibc-2.5-r0, 2.6.18-gentoo i686)
 =================================================================
 System uname: 2.6.18-gentoo i686 Intel(R) Pentium(R) 4 CPU 2.80GHz
 Gentoo Base System version 1.12.5
 Last Sync: Wed, 25 Oct 2006 07:50:01 +0000
 app-admin/eselect-compiler: [Not Present]
 dev-java/java-config: 1.3.7, 2.0.30
 dev-lang/python:     2.4.3-r4
 dev-python/pycrypto: 2.0.1-r5
 dev-util/ccache:     [Not Present]
 dev-util/confcache:  [Not Present]
 sys-apps/sandbox:    1.2.18.1
 sys-devel/autoconf:  2.13, 2.60
 sys-devel/automake:  1.4_p6, 1.5, 1.6.3, 1.7.9-r1, 1.8.5-r3, 1.9.6-r2, 1.10
 sys-devel/binutils:  2.17
 sys-devel/gcc-config: 1.3.14
 sys-devel/libtool:   1.5.22
 virtual/os-headers:  2.6.17-r1
 ACCEPT_KEYWORDS="x86 ~x86"
 AUTOCLEAN="yes"
 CBUILD="i686-pc-linux-gnu"
 CFLAGS="-march=pentium4 -O3 -msse2 -mfpmath=sse,387 -mmmx"
 CHOST="i686-pc-linux-gnu"
 CONFIG_PROTECT="/etc /usr/kde/3.5/env /usr/kde/3.5/share/config /usr/kde/3.5/shutdown /usr/share/X11/xkb /usr/share/config /var/qmail/alias /var/qmail/control"
 CONFIG_PROTECT_MASK="/etc/env.d /etc/env.d/java/ /etc/gconf /etc/java-config/vms/ /etc/revdep-rebuild /etc/terminfo /etc/texmf/web2c"
 CXXFLAGS="-march=pentium4 -O3 -msse2 -mfpmath=sse,387 -mmmx"
 DISTDIR="/usr/portage/distfiles"
 FEATURES="autoconfig distlocks metadata-transfer sandbox sfperms strict"
 GENTOO_MIRRORS="ftp://ftp-stud.fht-esslingen.de/pub/Mirrors/gentoo http://distfiles.gentoo.org http://www.ibiblio.org/pub/Linux/distributions/gentoo"
 LANG="de_DE"
 LC_ALL="de_DE"
 LINGUAS="de"
 MAKEOPTS="-j5"
 PKGDIR="/usr/portage/packages"
 PORTAGE_RSYNC_OPTS="--recursive --links --safe-links --perms --times --compress --force --whole-file --delete --delete-after --stats --timeout=180 --exclude=/distfiles --exclude=/local --exclude=/packages"
 PORTAGE_TMPDIR="/var/tmp"
 PORTDIR="/usr/portage"
 PORTDIR_OVERLAY="/usr/local/portage"
 SYNC="rsync://rsync.de.gentoo.org/gentoo-portage"
 USE="x86 X a52 acl acpi alsa amr apache2 artworkextra asf avahi bash-completion beagle berkdb bitmap-fonts browserplugin bzip2 cairo caps cddb cdr cli cracklib crypt cups curl dbus djvu dlloader dri dts dvd dvi eds elibc_glibc emboss encode esd exif expat fam fbcon ffmpeg fftw firefox flac fluidsynth fortran gdbm gif gimpprint gnome gnutls gpm gs gstreamer gtk gtkhtml gzip hal imagemagick imlib input_devices_keyboard input_devices_mouse isdnlog jack jack-tmpfs java jpeg jpeg2k kerberos kernel_linux lash ldap libg++ linguas_de logrotate mad mikmod mmap mmx mng mono mp3 mp4 mpeg mpm-worker mysql nautilus ncurses network nls nptl nptlonly nsplugin offensive ogg opengl pam pcre pdf perl png ppds pppd python qmail qt3 qt4 quicktime quota quotas readline real reflection rle samba sasl sdl session sndfile spell spl sqlite sse sse2 ssl svg swat t1lib tcl tcltk tcpd theora threads tidy tiff tk truetype truetype-fonts type1-fonts udev unicode urandom usb userland_GNU vcd video_cards_i810 vidix vorbis win32codecs wmf x264 xine xml xml2 xorg xpm xprint xv xvid xvmc xxmc zlib"
 Unset:  CTARGET, EMERGE_DEFAULT_OPTS, INSTALL_MASK, LDFLAGS, PORTAGE_RSYNC_EXTRA_OPTS


and everything works fine.

Starting from portage-2.1.2_pre3-r6 - and continuing to the latest version (2.1.2_pre-r8 as of this writing), it suddenly looks like this:

 asteria /usr/lib/portage # emerge --info     
 !!! No gcc found. You probably need to 'source /etc/profile'
 !!! to update the environment of this terminal and possibly
 !!! other terminals also.
 Portage 2.1.2_pre3-r8 (default-linux/x86/2006.1/desktop, [unavailable], glibc-2.5-r0, 2.6.18-gentoo i686)
 =================================================================
 System uname: 
 Gentoo Base System version 1.12.5
 Last Sync: Wed, 25 Oct 2006 07:50:01 +0000
 app-admin/eselect-compiler: [Not Present]
 dev-java/java-config: 1.3.7, 2.0.30
 dev-lang/python:     2.4.3-r4
 dev-python/pycrypto: 2.0.1-r5
 dev-util/ccache:     [Not Present]
 dev-util/confcache:  [Not Present]
 sys-apps/sandbox:    1.2.18.1
 sys-devel/autoconf:  2.13, 2.60
 sys-devel/automake:  1.4_p6, 1.5, 1.6.3, 1.7.9-r1, 1.8.5-r3, 1.9.6-r2, 1.10
 sys-devel/binutils:  2.17
 sys-devel/gcc-config: 1.3.14
 sys-devel/libtool:   1.5.22
 virtual/os-headers:  2.6.17-r1
 ACCEPT_KEYWORDS="x86 ~x86"
 AUTOCLEAN="yes"
 CBUILD="i686-pc-linux-gnu"
 CFLAGS="-march=pentium4 -O3 -msse2 -mfpmath=sse,387 -mmmx"
 CHOST="i686-pc-linux-gnu"
 CONFIG_PROTECT="/etc /usr/kde/3.5/env /usr/kde/3.5/share/config /usr/kde/3.5/shutdown /usr/share/X11/xkb /usr/share/config /var/qmail/alias /var/qmail/control"
 CONFIG_PROTECT_MASK="/etc/env.d /etc/env.d/java/ /etc/eselect/compiler /etc/gconf /etc/java-config/vms/ /etc/revdep-rebuild /etc/terminfo /etc/texmf/web2c"
 CXXFLAGS="-march=pentium4 -O3 -msse2 -mfpmath=sse,387 -mmmx"
 DISTDIR="/usr/portage/distfiles"
 FEATURES="autoconfig distlocks metadata-transfer sandbox sfperms strict"
 GENTOO_MIRRORS="ftp://ftp-stud.fht-esslingen.de/pub/Mirrors/gentoo http://distfiles.gentoo.org http://www.ibiblio.org/pub/Linux/distributions/gentoo"
 LANG="de_DE"
 LC_ALL="de_DE"
 LINGUAS="de"
 MAKEOPTS="-j5"
 PKGDIR="/usr/portage/packages"
 PORTAGE_RSYNC_OPTS="--recursive --links --safe-links --perms --times --compress --force --whole-file --delete --delete-after --stats --timeout=180 --exclude=/distfiles --exclude=/local --exclude=/packages"
 PORTAGE_TMPDIR="/var/tmp"
 PORTDIR="/usr/portage"
 PORTDIR_OVERLAY="/usr/local/portage"
 SYNC="rsync://rsync.de.gentoo.org/gentoo-portage"
 USE="x86 X a52 acl acpi alsa amr apache2 artworkextra asf avahi bash-completion beagle berkdb bitmap-fonts browserplugin bzip2 cairo caps cddb cdr cli cracklib crypt cups curl dbus djvu dlloader dri dts dvd dvi eds elibc_glibc emboss encode esd exif expat fam fbcon ffmpeg fftw firefox flac fluidsynth fortran gdbm gif gimpprint gnome gnutls gpm gs gstreamer gtk gtkhtml gzip hal imagemagick imlib input_devices_keyboard input_devices_mouse isdnlog jack jack-tmpfs java jpeg jpeg2k kerberos kernel_linux lash ldap libg++ linguas_de logrotate mad mikmod mmap mmx mng mono mp3 mp4 mpeg mpm-worker mysql nautilus ncurses network nls nptl nptlonly nsplugin offensive ogg opengl pam pcre pdf perl png ppds pppd python qmail qt3 qt4 quicktime quota quotas readline real reflection rle samba sasl sdl session sndfile spell spl sqlite sse sse2 ssl svg swat t1lib tcl tcltk tcpd theora threads tidy tiff tk truetype truetype-fonts type1-fonts udev unicode urandom usb userland_GNU vcd video_cards_i810 vidix vorbis win32codecs wmf x264 xine xml xml2 xorg xpm xprint xv xvid xvmc xxmc zlib"
 Unset:  CTARGET, EMERGE_DEFAULT_OPTS, INSTALL_MASK, LDFLAGS, PORTAGE_RSYNC_EXTRA_OPTS

In either case, the output of gcc-config looks like this:

 asteria /usr/lib/portage # gcc-config -c
 i686-pc-linux-gnu-4.1.1
 asteria /usr/lib/portage # gcc-config -E
 export PATH="/usr/i686-pc-linux-gnu/gcc-bin/4.1.1:/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/sbin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/opt/bin:/opt/sun-jdk-1.4.2.12/bin:/opt/sun-jdk-1.4.2.12/jre/bin:/opt/sun-jdk-1.4.2.12/jre/javaws:/usr/kde/3.5/sbin:/usr/kde/3.5/bin:/usr/qt/3/bin:/var/qmail/bin:/opt/bin:/opt/sun-jdk-1.4.2.12/bin:/opt/sun-jdk-1.4.2.12/jre/bin:/opt/sun-jdk-1.4.2.12/jre/javaws:/usr/kde/3.5/bin:/usr/qt/3/bin:/usr/games/bin:/var/qmail/bin"
 asteria /usr/lib/portage # gcc-config -B
 /usr/i686-pc-linux-gnu/gcc-bin/4.1.1
 asteria /usr/lib/portage # gcc-config -L
 /usr/lib/gcc/i686-pc-linux-gnu/4.1.1
 asteria /usr/lib/portage # gcc-config -X
 /usr/lib/gcc/i686-pc-linux-gnu/4.1.1/include/g++-v4

And, OF COURSE, /etc/profile is sourced in current shell. ;o)

revdep-rebuild -p shows no broken dependencies.