I run archlinux xfce4 with auto-login and auto start. After upgrading today 07-MAY-13 the X fails without leaving a error message in Xorg.0.log.  
Arclinux running xfce4 fails to start
arch linux;xorg;boot;xfce;fonts
The problem may be related to fonts and vector drawing in linux (cairo).If you auto-login and autostart like I do, the first thing to do is to stop athe autostart.In your ~/.bash-profile if there is a startxfce4 command, comment it out.#if [[ -z $DISPLAY ]] && ! [[ -e /tmp/.X11-unix/X0 ]] && (( EUID )); then#  exec nohup startxfce4 > .xlog & vlock#fiAlso check ~/.xinitrcYou may need to switch to an alternative console and login in as root, or login from a remote computer, or append systemd.unit=rescue.target to the kernel parameters inyour bootloader to do this.When done reboot and enter startxfce4 after reaching multi-user in boot.If you see libpng15.so.15: cannot open shared object file in the output, you likely have the vector drawing conflict, likely a cairo package from archlinux,org/AUR  installed to configure how your system does fonts..How to fix?A relatively easy way is too replace the fonts packages from archlinux,org/AUR with a new bundle by archlinux user bohoomil in the archlinux.org/wikias Infinality: the easy wayIf you are fussy about how fonts appear on the screen, be sure to read the form posts and the user notes before you decide to do this.The wiki covers what you you have to do, but look at these notes beore you start:You will be fundmentaly changing the way your archlinux uses fonts.You will have to add links in /etc/pacman.conf to his repositoryYou will likely have to remove some packages from archlinux,org/AUR but this will be done as part of the installation.Don't forget multilib if you run x86_64.Don't forget to run sudo pacman -Syy after updating 'pacman/conf'You may have to force (sudo pacman -Sd ) some package(s) installation.The pacman command for the bundle is sudo pacman -Syu infinality-bundleTo force install the pacman command is sudo pacman -Sd infinality-bundle  use with care!Good luck!As an example, here is my pacman.log from this morning [2013-05-07 11:09] [PACMAN] Running 'pacman -Syu cairo'[2013-05-07 11:09] [PACMAN] synchronizing package lists[2013-05-07 11:09] [PACMAN] starting full system upgrade[2013-05-07 11:09] [PACMAN] Running 'pacman -Syu cairo'[2013-05-07 11:09] [PACMAN] synchronizing package lists[2013-05-07 11:09] [PACMAN] starting full system upgrade[2013-05-07 11:10] [PACMAN] removed cairo-cleartype (1.12.2-1)[2013-05-07 11:10] [PACMAN] installed cairo (1.12.14-4)[2013-05-07 11:10] [PACMAN] Running 'pacman -Syu infinality-bundle'[2013-05-07 11:10] [PACMAN] synchronizing package lists[2013-05-07 11:10] [PACMAN] starting full system upgrade[2013-05-07 11:14] [PACMAN] Running 'pacman -Sd infinality-bundle'[2013-05-07 11:15] [PACMAN] removed freetype2-infinality (2.4.10-1)[2013-05-07 11:15] [ALPM-SCRIPTLET] [2013-05-07 11:15] [ALPM-SCRIPTLET]   Check for dead symlinks and leftover files [2013-05-07 11:15] [ALPM-SCRIPTLET]   in /etc/fonts/conf.d/[2013-05-07 11:15] [ALPM-SCRIPTLET]   [2013-05-07 11:15] [PACMAN] removed fontconfig (2.10.92-4)[2013-05-07 11:15] [ALPM] warning: /etc/fonts/conf.d/52-infinality.conf saved as /etc/fonts/conf.d/52-infinality.conf.pacsave[2013-05-07 11:15] [PACMAN] removed fontconfig-infinality (1-20130104)[2013-05-07 11:15] [PACMAN] removed cairo (1.12.14-4)[2013-05-07 11:15] [PACMAN] removed lib32-freetype2 (2.4.11-1)[2013-05-07 11:15] [PACMAN] removed lib32-fontconfig (2.10.92-1)[2013-05-07 11:15] [ALPM-SCRIPTLET]   If you have been using freetype2-infinality from the AUR,[2013-05-07 11:15] [ALPM-SCRIPTLET]   the runtime file that came with it has been saved as[2013-05-07 11:15] [ALPM-SCRIPTLET]   /etc/profile.d/infinality-settings.sh.pacsave and the new[2013-05-07 11:15] [ALPM-SCRIPTLET]   one was installed in its place. You can manually delete[2013-05-07 11:15] [ALPM-SCRIPTLET]   infinality-settings.sh.pacsave as it is not needed anymore.[2013-05-07 11:15] [ALPM-SCRIPTLET] [2013-05-07 11:15] [ALPM-SCRIPTLET]   If you are using [multilib], please install/upgrade[2013-05-07 11:15] [ALPM-SCRIPTLET]   lib32-freetype2-infinality-ultimate, too.[2013-05-07 11:15] [PACMAN] installed freetype2-infinality-ultimate (2.4.11-3)[2013-05-07 11:15] [ALPM-SCRIPTLET]   [2013-05-07 11:15] [ALPM-SCRIPTLET]   Fontconfig-ultimate configuration is done via [2013-05-07 11:15] [ALPM-SCRIPTLET]   /etc/fonts/conf.avail, /etc/fonts/conf.avail.infinality and [2013-05-07 11:15] [ALPM-SCRIPTLET]   conf.d. Read /etc/fonts/conf.d/README for more information.[2013-05-07 11:15] [ALPM-SCRIPTLET] [2013-05-07 11:15] [ALPM-SCRIPTLET]   Configuration via /etc/fonts/local.conf is still possible,[2013-05-07 11:15] [ALPM-SCRIPTLET]   but is no longer recommended for options available in conf.avail.[2013-05-07 11:15] [ALPM-SCRIPTLET] [2013-05-07 11:15] [ALPM-SCRIPTLET]   Main systemwide configuration should be done by symlinks, e.g.[2013-05-07 11:15] [ALPM-SCRIPTLET]   [2013-05-07 11:15] [ALPM-SCRIPTLET]   # cd /etc/fonts/conf.d[2013-05-07 11:15] [ALPM-SCRIPTLET]   # ln -s ../conf.avail/XX-foo.conf[2013-05-07 11:15] [ALPM-SCRIPTLET] [2013-05-07 11:15] [ALPM-SCRIPTLET]   In most cases default settings should suffice.[2013-05-07 11:15] [ALPM-SCRIPTLET] [2013-05-07 11:15] [ALPM-SCRIPTLET]   Custom user based configuration should be done in the same way,[2013-05-07 11:15] [ALPM-SCRIPTLET]   using XDG directory structure, e.g.[2013-05-07 11:15] [ALPM-SCRIPTLET] [2013-05-07 11:15] [ALPM-SCRIPTLET]   $ cd /root/.config/fontconfig/conf.d[2013-05-07 11:15] [ALPM-SCRIPTLET]   $ ln -s ../conf.avail/XX-foo.conf[2013-05-07 11:15] [ALPM-SCRIPTLET] [2013-05-07 11:15] [ALPM-SCRIPTLET]   A few examples can be found in[2013-05-07 11:15] [ALPM-SCRIPTLET]     /usr/share/doc/fontconfig/infinality-ultimate/fontconfig.[2013-05-07 11:15] [ALPM-SCRIPTLET]   [2013-05-07 11:15] [ALPM-SCRIPTLET]   For further information about fontconfig-infiinality-ultimate, see[2013-05-07 11:15] [ALPM-SCRIPTLET]     /usr/share/doc/fontconfig-infinality-ultimate/README.html[2013-05-07 11:15] [ALPM-SCRIPTLET]   Check also https://wiki.archlinux.org/index.php/Fonts.[2013-05-07 11:15] [ALPM-SCRIPTLET] [2013-05-07 11:15] [ALPM-SCRIPTLET] updating font cache... done.[2013-05-07 11:15] [PACMAN] installed fontconfig-infinality-ultimate (2.10.92-8)[2013-05-07 11:15] [PACMAN] installed cairo-infinality-ultimate (1.12.14-5)[2013-05-07 11:15] [PACMAN] installed lib32-freetype2-infinality-ultimate (2.4.11-2)[2013-05-07 11:15] [PACMAN] installed lib32-fontconfig-infinality-ultimate (2.10.92-2)[2013-05-07 11:18] [PACMAN] Running 'pacman -Syu lib32-freetype2-infinality-ultimate'[2013-05-07 11:18] [PACMAN] synchronizing package lists[2013-05-07 11:18] [PACMAN] starting full system upgrade[2013-05-07 11:18] [PACMAN] reinstalled lib32-freetype2-infinality-ultimate (2.4.11-2)