Calculating dependencies   ... done!

Dependencies could not be completely resolved due to
the following required packages not being installed:

x11-drivers/nvidia-drivers required by x11-base/xorg-server-1.3.0.0-r5
>=sys-devel/gcc-config-1.4 required by sys-devel/gcc-4.1.1-r3

Have you forgotten to run `emerge --update --newuse --deep world` prior to
depclean?  It may be necessary to manually uninstall packages that no longer
exist in the portage tree since it may not be possible to satisfy their
dependencies.  Also, be aware of the --with-bdeps option that is documented
in `man emerge`.