gnome-2.12 on ppc64?

[xyz]

I tried to emerge gnome-2.12 on my gentoo ppc64 with 64-bit userland, and did it successfully. The gnome env started normally but I couldn't use programes like nautilus, system monitor: their window frames
flickered continuously until the frames got away and left "naked" (without frames) behind, whenever I moved the mouse cursor over the buttons of the frames or icons on toolbars. I tried a terminal window too, it functioned as expected. I think it has something to do with gtk+-2.8.x, which I tried also under gnome-2.10 with the same problem. Is it a known problem with gtk+-2.8.x under ppc64, or a problem specific on my system?
Here is the emerge info:

Gentoo Base System version 1.6.13
Portage 2.0.51.22-r3 (default-linux/ppc/2005.1/ppc64/multilib, gcc-3.4.4, glibc-2.3.5-r2, 2.6.14-ck1 ppc64)
=================================================================
System uname: 2.6.14-ck1 ppc64 PPC970, altivec supported
ccache version 2.3 [disabled]
dev-lang/python: 2.3.5-r2, 2.4.1-r1
sys-apps/sandbox: 1.2.12
sys-devel/autoconf: 2.13, 2.59-r6
sys-devel/automake: 1.4_p6, 1.5, 1.6.3, 1.7.9-r1, 1.8.5-r3, 1.9.6-r1
sys-devel/binutils: 2.16.1
sys-devel/libtool: 1.5.18-r1
virtual/os-headers: 2.6.11-r2
ACCEPT_KEYWORDS="ppc64"
AUTOCLEAN="yes"
CBUILD="powerpc64-unknown-linux-gnu"
CFLAGS="-O3 -mcpu=G5 -mtune=970 -maltivec -mabi=altivec -mpowerpc64 -mpowerpc-gpopt -fsigned-char -pipe"
CHOST="powerpc64-unknown-linux-gnu"
CONFIG_PROTECT="/etc /usr/kde/2/share/config /usr/kde/3.3/env /usr/kde/3.3/share/config /usr/kde/3.3/shutdown /usr/kde/3.4/env /usr/kde/3.4/share/config /usr/kde/3.4/shutdown /usr/kde/3/share/config /usr/lib/X11/xkb /usr/lib64/mozilla/defaults/pref /usr/share/config /usr/share/texmf/dvipdfm/config/ /usr/share/texmf/dvips/config/ /usr/share/texmf/tex/generic/config/ /usr/share/texmf/tex/platex/config/ /usr/share/texmf/xdvi/ /var/qmail/control"
CONFIG_PROTECT_MASK="/etc/gconf /etc/terminfo /etc/env.d"
CXXFLAGS="-O3 -mcpu=G5 -mtune=970 -maltivec -mabi=altivec -mpowerpc64 -mpowerpc-gpopt -fsigned-char -pipe"
DISTDIR="/usr/portage/distfiles"
FEATURES="autoconfig distlocks sandbox sfperms strict"
GENTOO_MIRRORS="http://mirror.averse.net/pub/gentoo http://mirror.gentoo.gr.jp http://mymirror.asiaosc.org/gentoo/"
LANG="en_US.UTF-8"
LINGUAS="zh_CN en"
PKGDIR="/usr/portage/packages"
PORTAGE_TMPDIR="/var/tmp"
PORTDIR="/usr/portage"
SYNC="rsync://rsync.gentoo.org/gentoo-portage"
USE="ppc64 X aac aalib alsa altivec arts aspell berkdb bitmap-fonts cdr cjk crypt cups curl dba dvd dvdnav eds encode esd faac faad2 fam fb ffmpeg flac foomaticdb fortran gd gd-external gdbm gif gimpprint gnome gphoto2 gpm gstreamer gtk gtk2 imagemagick imlib ipv6 java jpeg ldap libwww mad motif mozilla mp3 mpeg mysql nas ncurses nls nptl nptlonly ogg opengl oss pam perl png python qt readline samba sdl slang spell ssl svg tcpd tetex theora tiff truetype truetype-fonts type1-fonts udev unicode v4l vidix vorbis xanim xine xml xml2 xmms xv xvmc zlib linguas_zh_CN linguas_en userland_GNU kernel_linux elibc_glibc"
Unset: ASFLAGS, CTARGET, LC_ALL, LDFLAGS, MAKEOPTS, PORTDIR_OVERLAY

Any help is much appreciated.

[xyz]

up