I follow the git/master on an HP Pavillion laptop, currently running a 3.1.2 kernel on what is basically a current slackware distibution.  The laptop has an ati-radian card (R200).   I built with debugging symbols and  ran 'gdb X' as root;  here's the backtrace:

Program received signal SIGSEGV, Segmentation fault.
0x080f4d86 in OpenConfigDir (path=0x81fef08 "%A,%R,/etc/X11/%R,%C/X11/%R,/etc/X11/%X,%C/X11/%X", cmdline=0x0, projroot=0x81feff0 "/usr", 
    confname=0x820a30a "xorg.conf.d") at scan.c:861
861                             free(list[num]);

[according to gdb num=-2 and list is 0x0]
(gdb) thread apply all bt full

Thread 1 (Thread 0xb745f7e0 (LWP 30196)):
#0  0x080f4d86 in OpenConfigDir (path=0x81fef08 "%A,%R,/etc/X11/%R,%C/X11/%R,/etc/X11/%X,%C/X11/%X", cmdline=0x0, projroot=0x81feff0 "/usr", 
    confname=0x820a30a "xorg.conf.d") at scan.c:861
        list = 0x0
        num = -2
        dirpath = 0x0
        pathcopy = 0x8918fe0 "%A"
        template = 0x8919008 "%C/X11/%X"
        found = 0
        cmdlineUsed = 0
#1  0x080f4f2e in xf86openConfigDirFiles (path=0x81fef08 "%A,%R,/etc/X11/%R,%C/X11/%R,/etc/X11/%X,%C/X11/%X", cmdline=0x0, projroot=0x81feff0 "/usr")
    at scan.c:956
No locals.
#2  0x080ba63a in xf86HandleConfigFile (autoconfig=0) at xf86Config.c:2328
        filename = 0xbfa9767c "\360<\221\b\300\031\\\267\320\003&\b\250v\251\277\370\376\t\b\f\301&\b@"
        dirname = 0x81ffc16 "Log file: \"%s\", Time: %s"
        sysdirname = 0x8919d70 "/usr/share/X11/xorg.conf.d"
        filesearch = 0x81fee74 "%A,%R,/etc/X11/%R,%P/etc/X11/%R,%E,%F,/etc/X11/%F,%P/etc/X11/%F,/etc/X11/%X,/etc/%X,%P/etc/X11/
%X.%H,%P/etc/X11/%X,%P/lib/X11/%X.%H,%P/lib/X11/%X"
        dirsearch = 0x81fef08 "%A,%R,/etc/X11/%R,%C/X11/%R,/etc/X11/%X,%C/X11/%X"
        filefrom = X_DEFAULT
        dirfrom = X_DEFAULT
        scanptr = 0xb759f5a0 "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n"
        singlecard = 0
        implicit_layout = 0
#3  0x080c2b09 in InitOutput (pScreenInfo=0x8272ca0, argc=1, argv=0xbfa97804) at xf86Init.c:365
        i = 0
        j = 0
        k = 136709072
        scr_index = -1219665935
        was_blocked = 0
        modulelist = 0x0
        optionlist = 0xb77e1820
        screenpix24 = 134735405
        pix24 = 3215554328
        pix24From = X_DEFAULT
        pix24Fail = 0
        autoconfig = 0
        configured_device = 0xb78c4ab8
#4  0x080631bc in main (argc=1, argv=0xbfa97804, envp=0xbfa9780c) at main.c:204
        i = 256
        alwaysCheckForInput = {0, 1}