Xorg hangs in Intrepid after waking up from locked screen

I have spent some time googling around for the issue I'm having, but have just found a mess of possibilities. I thought I'd ask here to see if anyone else has come across the same problem.

I'm running Ubuntu 8.10, and after my screen has been sitting locked for a while, when I come back to it, after I unlock the screen (type in my password), the Xserver hangs and appears to be in an infinite loop. The following error message appears:

[mi] EQ overflowing. The server is probably stuck in an infinite loop.
[mi] mieqEnequeue: out-of-order valuator event; dropping.

I just disabled the screensaver (fearing a problem with GL or something), but I don't know if that will work. The next time it locks up, I'll try getting a backtrace and figuring out what happens before the loop messages. This is, of course, assuming I have access to another machine with which to SSH to this laptop.

I'm on an Inspiron 640m. VGA module info from Xorg.log:
(II) LoadModule: "intel"

(II) Loading /usr/lib/xorg/modules/drivers//intel_drv.so
(II) Module intel: vendor="X.Org Foundation"
        compiled for 1.5.2, module version = 2.4.1
        Module class: X.Org Video Driver
        ABI class: X.Org Video Driver, version 4.1
(II) intel: Driver for Intel Integrated Graphics Chipsets: i810,
        i810-dc100, i810e, i815, i830M, 845G, 852GM/855GM, 865G, 915G,
        E7221 (i915), 915GM, 945G, 945GM, 945GME, 965G, G35, 965Q, 946GZ,
        965GM, 965GME/GLE, G33, Q35, Q33,
        Mobile Intel® GM45 Express Chipset,
        Intel Integrated Graphics Device, G45/G43, Q45/Q43
(II) Primary Device is: PCI 00@00:02:0

From lspci -vnn:
00:02.0 VGA compatible controller [0300]: Intel Corporation Mobile 945GM/GMS, 943/940GML Express Integrated Graphics Controller [8086:27a2] (rev 03)
        Subsystem: Dell Device [1028:01d8]
        Flags: bus master, fast devsel, latency 0, IRQ 16
        Memory at eff00000 (32-bit, non-prefetchable) [size=512K]
        I/O ports at eff8 [size=8]
        Memory at d0000000 (32-bit, prefetchable) [size=256M]
        Memory at efec0000 (32-bit, non-prefetchable) [size=256K]
        Capabilities: [90] Message Signalled Interrupts: Mask- 64bit- Queue=0/0 Enable-
        Capabilities: [d0] Power Management version 2
        Kernel modules: intelfb

00:02.1 Display controller [0380]: Intel Corporation Mobile 945GM/GMS/GME, 943/940GML Express Integrated Graphics Controller [8086:27a6] (rev 03)
        Subsystem: Dell Device [1028:01d8]
        Flags: bus master, fast devsel, latency 0
        Memory at eff80000 (32-bit, non-prefetchable) [size=512K]
        Capabilities: [d0] Power Management version 2

Some bits of dmesg RE: graphics driver:
[ 19.056181] Linux agpgart interface v0.103
[ 19.135069] agpgart-intel 0000:00:00.0: Intel 945GM Chipset
[ 19.135664] agpgart-intel 0000:00:00.0: detected 7932K stolen memory
[ 19.152560] agpgart-intel 0000:00:00.0: AGP aperture is 256M @ 0xd0000000

If there's anything else I can post to help, let me know.