[blocks B     ] <sys-apps/portage-2.1.7.16 ("<sys-apps/portage-2.1.7.16" is blocking app-shells/bash-4.1_p9)
[blocks B     ] <sys-apps/util-linux-2.13 ("<sys-apps/util-linux-2.13" is blocking sys-apps/coreutils-8.5)
[blocks B     ] >=dev-lang/python-2.6.6:2.6 (">=dev-lang/python-2.6.6:2.6" is blocking sys-apps/portage-2.1.6.13)
[blocks B     ] sys-apps/mktemp ("sys-apps/mktemp" is blocking sys-apps/coreutils-8.5)
[blocks B     ] <sys-apps/portage-2.1.9 ("<sys-apps/portage-2.1.9" is blocking dev-lang/python-2.6.6-r1)
[blocks B     ] >=sys-apps/coreutils-6.10 (">=sys-apps/coreutils-6.10" is blocking sys-apps/mktemp-1.5)

 * Error: The above package list contains packages which cannot be
 * installed at the same time on the same system.

  ('binary', '/', 'sys-apps/coreutils-8.5', 'merge') pulled in by
    >=sys-apps/coreutils-6.4 required by ('binary', '/', 'sys-apps/portage-2.1.9.25', 'merge')
    sys-apps/coreutils required by ('binary', '/', 'app-admin/eselect-1.2.11', 'merge')

  ('binary', '/', 'app-shells/bash-4.1_p9', 'merge') pulled in by
    >=app-shells/bash-3.2_p17 required by ('binary', '/', 'sys-apps/portage-2.1.9.25', 'merge')

  ('binary', '/', 'dev-lang/python-2.6.6-r1', 'merge') pulled in by
    dev-lang/python:2.6 required by ('binary', '/', 'sys-apps/portage-2.1.9.25', 'merge')


For more information about Blocked Packages, please refer to the following
section of the Gentoo Linux x86 Handbook (architecture is irrelevant):