god ~ # emerge -uavDN world

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

Calculating world dependencies... done!

[blocks B     ] sys-apps/coldplug (is blocking sys-fs/udev-103)
[blocks B     ] >=sys-fs/udev-089 (is blocking sys-apps/coldplug-20040920-r1)
[ebuild     U ] sys-apps/portage-2.1.1-r2 [2.1.1-r1] USE="-build -doc (-selinux)" LINGUAS="-pl" 5 kB 
*** Portage will stop merging at this point and reload itself,
    then resume the merge.
[ebuild  N    ] virtual/mysql-5.0  0 kB 
[ebuild     U ] sys-fs/udev-103 [087-r1] USE="(-selinux)" 195 kB 
[ebuild  NS   ] sys-kernel/gentoo-sources-2.6.18-r3  USE="-build -symlink (-ultra1)" 228 kB 
[ebuild     U ] net-nds/openldap-2.3.27-r3 [2.3.27-r2] USE="berkdb crypt gdbm ipv6 perl readline sasl ssl tcpd -debug -kerberos -minimal -odbc -overlays -samba (-selinux) -slp -smbkrb5passwd" 0 kB 
[ebuild  NS   ] dev-db/phpmyadmin-2.9.1.1  USE="vhosts" 1,509 kB 

Total size of downloads: 1,938 kB

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

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

http://www.gentoo.org/doc/en/handbook/handbook-x86.xml?full=1#blocked