Xorg wouldn't start with latest updates.

One of these in my Xorg.0.log after upgrading to latest mesa ati-dri and libgl

[    27.289] 0: /usr/bin/X (xorg_backtrace+0x28) [0x49f1a8]
[    27.289] 1: /usr/bin/X (0x400000+0x60239) [0x460239]
[    27.289] 2: /lib/libpthread.so.0 (0x7f42d79da000+0xf1c0) [0x7f42d79e91c0]
[    27.289] Segmentation fault at address (nil)


Removing 'nomodeset' from /boot/grub/menu.lst fixes it.