slacker ~ # emerge -uDav world

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

Calculating world dependencies         e
!!! Packages for the following atoms are either all
!!! masked or don't exist:
x11-drivers/xf86-video-v4l

... done!
[blocks B     ] x11-libs/libXft (is blocking x11-base/xorg-x11-6.8.2-r6)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking x11-apps/xrdb-1.0.1)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking x11-wm/twm-1.0.1)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking x11-proto/randrproto-1.1.2)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking x11-libs/libXinerama-1.0.1)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking x11-libs/libXrandr-1.1.0.2-r1)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking media-fonts/font-adobe-utopia-75dpi-1.0.1)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking x11-apps/xset-1.0.1)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking x11-libs/libXv-1.0.1)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking media-fonts/font-bh-lucidatypewriter-100dpi-1.0.0)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking x11-libs/libXprintUtil-1.0.1)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking media-fonts/font-bh-lucidatypewriter-75dpi-1.0.0)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking x11-libs/libXprintAppUtil-1.0.1)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking x11-libs/libXdamage-1.0.2.2)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking media-fonts/font-bitstream-100dpi-1.0.0)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking x11-libs/libXxf86dga-1.0.0-r1)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking media-fonts/font-bh-75dpi-1.0.0)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking x11-libs/libXevie-1.0.0-r1)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking media-fonts/font-adobe-utopia-100dpi-1.0.1)
[blocks B     ] x11-plugins/compiz-plugin-opacity (is blocking x11-wm/compiz-0.0.7_alpha20060318)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking x11-libs/libXcomposite-0.2.2.2)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking x11-libs/libXScrnSaver-1.0.1-r1)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking media-fonts/font-adobe-100dpi-1.0.0)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking x11-libs/libXvMC-1.0.1)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking x11-libs/libXfontcache-1.0.1-r1)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking media-fonts/font-bh-100dpi-1.0.0)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking media-fonts/font-ibm-type1-1.0.0)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking media-fonts/font-adobe-75dpi-1.0.0)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking x11-libs/libXTrap-1.0.0)
[blocks B     ] <=x11-base/xorg-x11-6.9 (is blocking media-fonts/font-bitstream-75dpi-1.0.0)
[ebuild     U ] sys-apps/man-1.6c [1.6b-r2] USE="nls" 239 kB
[ebuild     U ] x11-libs/libdrm-2.1_alpha20060313 [2.0] USE="-debug" 0 kB [1]
[ebuild     U ] media-libs/mesa-6.5.0_alpha20060317 [6.5.0_alpha20060308] USE="-debug -motif" VIDEO_CARDS="-ati -i810 -mga -none -s3virge -savage -sis -tdfx -trident -via" 0 kB [1]
[ebuild     UD] x11-base/xorg-x11-6.8.2-r6 [7.0-r1] USE="bitmap-fonts% cjk% font-server% ipv6% nls% opengl% pam% truetype-fonts% type1-fonts% xv% -debug% -dlloader% -dmx% -doc% -insecure-drivers% -minimal% -nocxx% -sdk% -static% -xprint%" 0 kB
[ebuild  N    ] virtual/x11-6.8  0 kB
[ebuild     U ] x11-libs/qt-3.3.4-r9 [3.3.4-r8] USE="cups gif immqt-bc ipv6 opengl sqlite xinerama -debug -doc -examples -immqt -mysql -nas -odbc -postgres" 0 kB
[ebuild     U ] x11-wm/compiz-0.0.7_alpha20060318 [0.0.5_alpha20060308] USE="gnome kde svg -intel_copy_pixel% -paint_patch% -switch_all_desktops" 0 kB [1]

Total size of downloads: 239 kB
Portage overlays:
 [1] /usr/local/xgloverlay

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

slacker ~ #