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

Calculating dependencies... done!
[ebuild     U  ] x11-proto/inputproto-2.0.2 [2.0.1] 152 kB
[ebuild     U  ] x11-libs/libXi-1.4.3 [1.4.2] USE="-doc -static-libs" 413 kB
[ebuild     U  ] sys-apps/dbus-1.4.10 [1.4.8-r1] USE="X -debug -doc (-selinux) -static-libs -test" 1,819 kB
[ebuild     U  ] dev-libs/dbus-glib-0.94 [0.92] USE="bash-completion -debug -doc -static-libs -test" 690 kB
[ebuild     U  ] sys-devel/make-3.82-r1 [3.82] USE="nls -static" 0 kB
[ebuild     UD ] sys-fs/udev-168-r2 [171-r1] USE="extras%* (-selinux) -test (-acl%*) (-action_modeswitch%) (-debug%) (-edd%) (-floppy%) (-gudev%*) (-hwdb%*) (-introspection%*) (-keymap%*) (-rule_generator%*)" 0 kB
[ebuild     U  ] dev-java/sun-jre-bin-1.6.0.26 [1.6.0.25] USE="X alsa nsplugin -jce -odbc" 83,478 kB
[ebuild     U  ] dev-java/sun-jdk-1.6.0.26 [1.6.0.25] USE="X alsa doc examples nsplugin -derby -jce -odbc" 0 kB
[ebuild     U  ] net-wireless/bluez-4.94-r1 [4.94] USE="alsa consolekit cups gstreamer usb -caps -debug -health -maemo6 -old-daemons -pcmcia -pnat -test-programs" 0 kB
[ebuild     U  ] x11-drivers/xf86-video-intel-2.15.0-r1 [2.15.0] USE="dri" 0 kB
[ebuild  NS    ] sys-kernel/gentoo-sources-2.6.39-r1 [2.6.38-r5, 2.6.39] USE="symlink -build -deblob" 72 kB
[ebuild     U  ] sys-kernel/dracut-010-r2 [010-r1] USE="-debug (-selinux)" DRACUT_MODULES="-biosdevname -btrfs -caps -crypt -dmraid -dmsquash-live -gensplash -iscsi -lvm -mdraid -multipath -nbd -nfs -plymouth -syslog -xen" 0 kB
[ebuild     U  ] sys-kernel/genkernel-3.4.16 [3.4.15] USE="bash-completion (-ibm) (-selinux)" 203 kB
[ebuild     U  ] sys-power/upower-0.9.11-r1 [0.9.11] USE="introspection -debug -doc -ios" 0 kB

Total: 14 packages (12 upgrades, 1 downgrade, 1 in new slot), Size of downloads: 86,825 kB

!!! Multiple package instances within a single package slot have been pulled
!!! into the dependency graph, resulting in a slot conflict:

sys-fs/udev:0

  (sys-fs/udev-171-r1::gentoo, installed) pulled in by
    >=sys-fs/udev-171[gudev] required by (sys-power/upower-0.9.11-r1::gentoo, ebuild scheduled for merge)
    (and 4 more with the same problem)

  (sys-fs/udev-168-r2::gentoo, ebuild scheduled for merge) pulled in by
    >=sys-fs/udev-145[extras] required by (gnome-base/gvfs-1.8.1::gnome, installed)
    (and 6 more with the same problem)


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. You may want to try a larger value of
the --backtrack option, such as --backtrack=30, in order to see if
that will solve this conflict automatically.

For more information, see MASKED PACKAGES section in the emerge man
page or refer to the Gentoo Handbook.