dmesg:
Linux version 2.6.32-gentoo (root@frodo) (gcc version 4.4.2 (Gentoo 4.4.2 p1.0) ) #1 PREEMPT
  Sat Dec 12 10:35:31 EST 2009
rtc_cmos 00:03: setting system clock to 2010-01-11 06:13:14 UTC (1263190394)

Xorg.?.log have message have intel errors.

Xorg start info:
X.Org X Server 1.7.4
Release Date: 2010-01-08
X Protocol Version 11, Revision 0
Build Operating System: Linux 2.6.32-gentoo i686 
Current Operating System: Linux frodo 2.6.32-gentoo #1 PREEMPT Sat Dec 12 10:35:31 EST 2009 i686
Kernel command line: root=/dev/sda8 vmalloc=200M video=intelfb:1680x1050-32@60,vram=32,mtrr vga=0xF05 fbcon=font:vga8x8
Build Date: 11 January 2010  06:36:19AM

Xorg Driver info:
(II) LoadModule: "dri2"
(II) Loading /usr/lib/xorg/modules/extensions/libdri2.so
(II) Module dri2: vendor="X.Org Foundation"
	compiled for 1.7.4, module version = 1.1.0
	ABI class: X.Org Server Extension, version 2.0
(II) Loading extension DRI2
(II) LoadModule: "intel"
(II) Loading /usr/lib/xorg/modules/drivers/intel_drv.so
(II) Module intel: vendor="X.Org Foundation"
	compiled for 1.7.3.902, module version = 2.10.0
	Module class: X.Org Video Driver
	ABI class: X.Org Video Driver, version 6.0
(II) LoadModule: "radeonhd"
(II) Loading /usr/lib/xorg/modules/drivers/radeonhd_drv.so
(II) Module radeonhd: vendor="AMD GPG"
	compiled for 1.7.3, module version = 1.3.0
	Module class: X.Org Video Driver
	ABI class: X.Org Video Driver, version 6.0
(II) LoadModule: "evdev"
(II) Loading /usr/lib/xorg/modules/input/evdev_drv.so
(II) Module evdev: vendor="X.Org Foundation"
	compiled for 1.7.3.901, module version = 2.3.2
	Module class: X.Org XInput Driver
	ABI class: X.Org XInput driver, version 7.0
 
Xorg errors:
(WW) intel(0): i830_uxa_prepare_access: gtt bo map failed: Input/output error
(EE) intel(0): Failed to submit batch buffer, expect rendering corruption or even a frozen display: Input/output error.
(EE) intel(0): Failed to submit batch buffer, expect rendering corruption or even a frozen display: Input/output error.
... continues at length ...
All X consoles frozen, system requires reboot.

kern.log has:
Jan 13 02:29:05 frodo kernel: device eth1 left promiscuous mode 	<<==== exiting from etherape
Jan 13 05:04:15 frodo kernel: [drm:i915_hangcheck_elapsed] *ERROR* Hangcheck timer elapsed... GPU hung
Jan 13 05:04:15 frodo kernel: render error detected, EIR: 0x00000000
Jan 13 05:04:15 frodo kernel: i915: Waking up sleeping processes
Jan 13 05:04:15 frodo kernel: [drm:i915_wait_request] *ERROR* i915_wait_request returns -5 (awaiting 79150277 at 79150273)
Jan 13 05:04:15 frodo kernel: reboot required
Jan 13 05:04:16 frodo kernel: [drm:i915_gem_execbuffer] *ERROR* Execbuf while wedged
Jan 13 05:04:16 frodo kernel: [drm:i915_gem_execbuffer] *ERROR* Execbuf while wedged
... continues at length...

I believe there is a 1:1 relationship between the "i915_gem_execbuffer" errors
and the "Failed to submit batch buffer" errrors.

The error seemed to suggest uxa was involved.  So Xorg was rebooted with the
  Option "AccelMethod" "UXA" disabled in xorg.conf.  Still did not fix the problem.