[gentoo-user] Xorg segfaults, but GDM welcome screen loads

[Grant]

Yesterday I caught up with portage and updated quite a few packages on
a remote workstation.  The system hadn't been updated for about a
month.  The updates included some xorg stuff and some xfce4 stuff.
Today when the workstation's user logged in via gdm, she clicked the
xfce4 "Migrate Config" option, something weird happened, and she ended
up back on the gdm welcome screen.  Now whenever she logs is via gdm,
the screen immediately goes black and she is routed back to the gdm
welcome screen again.  When I have grsecurity enabled I get this in
dmesg:

Segmentation fault occurred at 000068e453633fdc in
/usr/bin/Xorg[X:4777] uid/euid:0/0 gid/egid:0/0, parent
/usr/sbin/gdm-binary[gdm:4775] uid/euid:0/0 gid/egid:1010/1002

She also tried skipping gdm and issuing startxfce4 manually but it
fails in a similar way and displays "disconnected from session
manager".  I get this in Xorg.0.log:

Backtrace:
[    74.799] 0: /usr/bin/X (xorg_backtrace+0x28) [0x49eeb8]
[    74.799] 1: /usr/bin/X (0x400000+0x62849) [0x462849]
[    74.799] 2: /lib/libpthread.so.0 (0x64727eac2000+0xf3f0) [0x64727ead13f0]
[    74.800] 3: /usr/lib64/xorg/modules/drivers/nv_drv.so
(0x64727bed7000+0x112d0) [0x64727bee82d0]
[    74.800] 4: /usr/lib64/xorg/modules/libshadowfb.so
(0x64727a682000+0x3db2) [0x64727a685db2]
[    74.800] 5: /usr/bin/X (0x400000+0x2da29) [0x42da29]
[    74.800] 6: /usr/bin/X (0x400000+0x2eda9) [0x42eda9]
[    74.800] 7: /usr/bin/X (0x400000+0x2475a) [0x42475a]
[    74.800] 8: /lib/libc.so.6 (__libc_start_main+0xe6) [0x64727dcb2ba6]
[    74.800] 9: /usr/bin/X (0x400000+0x242f9) [0x4242f9]
[    74.800] Segmentation fault at address 0x64727462bfdc
[    74.800]
Fatal server error:
[    74.800] Caught signal 11 (Segmentation fault). Server aborting

and when grsecurity is enabled I get this in dmesg:

Segmentation fault occurred at 000064727462bfdc in
/usr/bin/Xorg[X:4647] uid/euid:1003/0 gid/egid:1010/1010, parent
/usr/bin/xinit[xinit:4646] uid/euid:1003/1003 gid/egid:1010/1010

I have tried disabling all security options in the kernel but I get
the same results with the exception of the dmesg info.  I tried
re-emerging xorg-server, xf86-video-nv, xinit, and gdm.  Strangely,
after re-emerging xorg-server and xinit there were files to change in
etc-update.  I don't see how that's possible since I'm caught up with
emerge -DuN world.  revdep-rebuild comes up with nothing.  I'm running
an emerge -e world now.  It's weird that the gdm welcome screen will
load (which implies xorg) but nothing afterward.  Any ideas?

- Grant