Вопрос по emerge world... [SOLVED]

# emerge world -pvuD выдает:
Calculating dependencies... done!
[ebuild U ] dev-libs/xerces-c-2.8.0 [2.7.0-r1] USE="iconv%* threads%* -debug% -doc -icu% -libwww%" 0 kB
[ebuild U ] media-libs/musicbrainz-2.1.5 [2.1.4] 512 kB
[ebuild U ] app-emulation/qemu-softmmu-0.9.1-r1 [0.9.0-r4] USE="alsa sdl -gnutls% -kqemu" 0 kB
[ebuild N ] app-accessibility/orca-2.22.1 USE="-debug" 0 kB
[ebuild N ] app-accessibility/gok-1.3.7 USE="X usb -debug -doc" 0 kB
[ebuild N ] app-accessibility/dasher-4.7.3 USE="accessibility gnome -cairo -debug" 0 kB
Total: 6 packages (3 upgrades, 3 new), Size of downloads: 512 kB
!!! Multiple versions within a single package slot have been pulled
!!! into the dependency graph, resulting in a slot conflict:
dev-libs/xerces-c:0
('installed', '/', 'dev-libs/xerces-c-2.7.0-r1', 'nomerge') pulled in by
@world
('installed', '/', 'dev-libs/xalan-c-1.10.0', 'nomerge')
('ebuild', '/', 'dev-libs/xerces-c-2.8.0', 'merge') pulled in by
('installed', '/', 'app-emulation/virtualbox-1.5.6', 'nomerge')
@world
('installed', '/', 'games-strategy/glest-2.0.1', 'nomerge')
It may be possible to solve this problem by using package.mask to
prevent one of those packages from being selected. However, it is also
possible that conflicting dependencies exist such that they are
impossible to satisfy simultaneously. If such a conflict exists in the
dependencies of two different packages, then those packages can not be
installed simultaneously.
For more information, see MASKED PACKAGES section in the emerge man page
or refer to the Gentoo Handbook.
Что это? И еще как избавиться от того чтобы при emerge world не собирались пакеты gok, orca и dasher