Both Gnuman and Mepis.org mentions that you should be carefull with Xorg-core update as it breaks X
Here at Mepis.org
and Gnuman as well
For those who are using Ubuntu, Kubuntu and Xubuntu are effected. Please be aware that there is a problem when updating xorg-core.
The latest update breaks X (X allows desktop environments to run (Gnome, KDE, etc…)) and there is a workaround, or better yet if you see this update, DO NOT UPDATE.
There is a workaround for those who have applied this fix which can be found at Ubuntu Forums .
Workaround – http://ubuntuforums.org/showthread.php?t=240957