Forwarding this bug from Ubuntu reporter jean-baptiste:
http://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-ati/+bug/446674

[Problem]
With the mesa 7.6.0 release, a corrupted low memory error appears in dmesg.  Both stellarium and googleearth crash.  Downgrading back to a git snapshot of mesa from mid-August makes these problems go away.

[Original Description]
hello,
after the update to mesa 7.6.0-1ubuntu1 this is impossible to launch stellarium or google earth.

jb@furious:~$ stellarium
 ------------------------------------------------------- 
[ This is Stellarium 0.10.2 - http://www.stellarium.org ] 
[ Copyright (C) 2000-2009 Fabien Chereau et al          ] 
 ------------------------------------------------------- 
Writing log file to: "/home/jb/.stellarium/log.txt" 
File search paths: 
  0 .  "/home/jb/.stellarium" 
  1 .  "/usr/share/stellarium" 
Config file is:  "/home/jb/.stellarium/config.ini" 
Erreur de segmentation (core dumped)

The probleme appear just after the upgrade
have a nice day and ask me for more question
jb

Architecture: i386
Date: Fri Oct  9 07:15:06 2009
DistroRelease: Ubuntu 9.10
MachineType: IBM 2374K1G
Package: xorg 1:7.4+3ubuntu5
PccardctlIdent:
 Socket 0:
   no product info available
 Socket 1:
   no product info available
PccardctlStatus:
 Socket 0:
   no card
 Socket 1:
   no card
ProcCmdLine: root=UUID=272fe164-c2c9-448f-950b-fe6369af86ea ro quiet splash
ProcEnviron:
 LANGUAGE=fr_FR.UTF-8
 LANG=fr_FR.UTF-8ProcVersionSignature: Ubuntu 2.6.31-12.41-generic
RelatedPackageVersions:
 xserver-xorg 1:7.4+3ubuntu5
 libgl1-mesa-glx 7.6.0-1ubuntu1
 libdrm2 2.4.13-1ubuntu1
 xserver-xorg-video-intel 2:2.8.1-1ubuntu3
 xserver-xorg-video-ati 1:6.12.99+git20090825.fc74e119-0ubuntu3
SourcePackage: xorg
Uname: Linux 2.6.31-12-generic i686
XsessionErrors:
 (gnome-settings-daemon:2004): GLib-CRITICAL **: g_propagate_error: assertion `src != NULL' failed
 (gnome-settings-daemon:2004): GLib-CRITICAL **: g_propagate_error: assertion `src != NULL' failed
 (polkit-gnome-authentication-agent-1:2247): GLib-CRITICAL **: g_once_init_leave: assertion `initialization_value != 0' failed
 (nautilus:2234): Eel-CRITICAL **: eel_preferences_get_boolean: assertion `preferences_is_initialized ()' failed
 (gnome-panel:2124): Gdk-WARNING **: /build/buildd/gtk+2.0-2.18.2/gdk/x11/gdkdrawable-x11.c:952 drawable is not a pixmap or window
dmi.bios.date: 03/29/2005
dmi.bios.vendor: IBM
dmi.bios.version: 1RETDJWW (3.15 )
dmi.board.name: 2374K1G
dmi.board.vendor: IBM
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: IBM
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnIBM:bvr1RETDJWW(3.15):bd03/29/2005:svnIBM:pn2374K1G:pvrThinkPadT42:rvnIBM:rn2374K1G:rvrNotAvailable:cvnIBM:ct10:cvrNotAvailable:
dmi.product.name: 2374K1G
dmi.product.version: ThinkPad T42
dmi.sys.vendor: IBM
system: architecture:       i686kernel:             2.6.31-12-generic

[ 361.000976] Corrupted low memory at c00029bc (29bc phys) = 78bcbc7d

[15771.019435] stellarium[4571]: segfault at 1862677 ip 0180eb43 sp
bf8ed7a0 error 7 in radeon_dri.so[17be000+24f000]
[16027.985503] stellarium[4596]: segfault at 460b677 ip 045b7b43 sp
bfd549a0 error 7 in radeon_dri.so[4567000+24f000]
[16094.972517] stellarium[4640]: segfault at 4bef677 ip 04b9bb43 sp
bf827aa0 error 7 in radeon_dri.so[4b4b000+24f000]
[16466.158885] stellarium[5589]: segfault at 6892677 ip 0683eb43 sp
bf9bf520 error 7 in radeon_dri.so[67ee000+24f000]

[18757.154000] googleearth-bin: page allocation failure. order:4, mode:0x40d0
[18757.154008] Pid: 6983, comm: googleearth-bin Tainted: G W 2.6.31-12-generic #41-Ubuntu
[18757.154011] Call Trace:
[18757.154026] [<c0568fde>] ? printk+0x18/0x1a
[18757.154033] [<c01b3a00>] __alloc_pages_slowpath+0x340/0x480
[18757.154038] [<c01b3c4f>] __alloc_pages_nodemask+0x10f/0x120
[18757.154042] [<c01b3ca7>] __get_free_pages+0x17/0x30
[18757.154047] [<c01dbfaf>] __kmalloc+0xdf/0x180
[18757.154086] [<f0ea1e48>] radeon_cp_cmdbuf+0xa98/0xbf0 [radeon]
[18757.154093] [<c03143f8>] ? copy_from_user+0x38/0x130
[18757.154123] [<f07da6c0>] drm_ioctl+0x180/0x360 [drm]
[18757.154146] [<f0ea13b0>] ? radeon_cp_cmdbuf+0x0/0xbf0 [radeon]
[18757.154151] [<c0310416>] ? rb_insert_color+0x76/0x100
[18757.154157] [<c012e9b1>] ? __dequeue_entity+0x21/0x40
[18757.154166] [<c01f0413>] vfs_ioctl+0x73/0x90
[18757.154169] [<c01f06e1>] do_vfs_ioctl+0x71/0x310
[18757.154173] [<c01f09df>] sys_ioctl+0x5f/0x80
[18757.154178] [<c010334c>] syscall_call+0x7/0xb

i notice also this:
jb@furious:~$ glxgears
*********************************WARN_ONCE*********************************
File radeon_tcl.c function radeon_run_tcl_render line 499
Rendering was 79 commands larger than predicted size. We might overflow command buffer.
***************************************************************************
6536 frames in 5.0 seconds