Маскинг ядра и не только...

Все правильно. Ты же сказал ему, что r5 и больше тебе не нужны, вот он и впихивает пакет с максимальной версией из разрешенных.
Напиши просто:
sys-kernel/gentoo-sources
и замаскишь все доступные версии ядра.
_________________
Toshiba Portege 3490CT
Pentium 3 (Coppermine) 733 Mhz, 256 Mb RAM, 20 Gb HD
Kernel: 2.6.15.1 (Suspend2 patch)
Gentoo Base System 1.12.0-pre15
Enlightenment DR 17 (cvs head)

Получается следующее:

base ~ # emerge -uDp world

These are the packages that I would merge, in order:

Calculating world dependencies al
!!! All ebuilds that could satisfy "sys-kernel/gentoo-sources" have been masked.
!!! One of the following masked packages is required to complete your request:
- sys-kernel/gentoo-sources-2.6.14-r5 (masked by: package.mask)
- sys-kernel/gentoo-sources-2.6.15-r4 (masked by: package.mask)
- sys-kernel/gentoo-sources-2.4.31-r1 (masked by: package.mask)
- sys-kernel/gentoo-sources-2.6.15-r2 (masked by: package.mask)
- sys-kernel/gentoo-sources-2.6.15-r3 (masked by: package.mask)
- sys-kernel/gentoo-sources-2.6.15-r1 (masked by: package.mask)
- sys-kernel/gentoo-sources-2.6.14-r7 (masked by: package.mask)
- sys-kernel/gentoo-sources-2.6.15 (masked by: package.mask)
- sys-kernel/gentoo-sources-2.4.32-r2 (masked by: package.mask)
- sys-kernel/gentoo-sources-2.6.15-r5 (masked by: package.mask)

For more information, see MASKED PACKAGES section in the emerge man page or
refer to the Gentoo Handbook.
(dependency required by "media-libs/alsa-lib-1.0.11_rc3" [ebuild])

!!! Problem resolving dependencies for sys-apps/portage
!!! Depgraph creation failed.