Computed crashed after trying to log switch to another user through GDM

Thread 1 (process 7802):
#0 0x00cc6422 in __kernel_vsyscall ()
No symbol table info available.
#1 0x003b1601 in *__GI_raise (sig=6)
    at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
 resultvar = <value optimized out>
 pid = 5074932
 selftid = 7802
#2 0x003b4a62 in *__GI_abort () at abort.c:92
 act = {__sigaction_handler = {
    sa_handler = 0xb8f4e4 <_rtld_local+1220>,
    sa_sigaction = 0xb8f4e4 <_rtld_local+1220>}, sa_mask = {__val = {917504,
      136066896, 134582228, 3213672264, 39520, 3213672232, 134544804,
      134532708, 1031, 12122360, 4508129, 1031, 136066896, 3213672160,
      5074932, 15, 3213673620, 3213672280, 4627156, 2, 3213672160, 4, 0,
      3213672256, 3213672268, 2, 4933319, 4933315, 4928865, 4928891, 230,
      3213672160}}, sa_flags = -1081295064, sa_restorer = 0x4b5a63}
 sigs = {__val = {32, 0 <repeats 31 times>}}
#3 0x003e856d in __libc_message (do_abort=2,
    fmt=0x4b78b8 "*** glibc detected *** %s: %s: 0x%s ***\n")
    at ../sysdeps/unix/sysv/linux/libc_fatal.c:189
 ap = <value optimized out>
 fd = -1081294704
 on_2 = <value optimized out>
 list = <value optimized out>
 nlist = <value optimized out>
 cp = <value optimized out>
 written = false
#4 0x003f2611 in malloc_printerr (action=<value optimized out>,
    str=0x6 <Address 0x6 out of bounds>, ptr=0x96a6dd0) at malloc.c:6264
 buf = "096a6dd0"
 cp = <value optimized out>
#5 0x003f81e8 in *__GI___libc_realloc (oldmem=0x0, bytes=512)
    at malloc.c:3778
 ar_ptr = <value optimized out>
 nb = 157999728
 newp = <value optimized out>
 oldp = (const mchunkptr) 0x96a6dc8
 oldsize = 0
 __func__ = "__libc_realloc"
#6 0x080aa523 in Xrealloc ()

ProblemType: Crash
Architecture: i386
AssertionMessage: *** glibc detected *** /usr/bin/X: realloc(): invalid pointer: 0x096a6dd0 ***
CurrentDmesg:
 [ 24.780015] eth1: no IPv6 routers present
 [ 35.908042] end_request: I/O error, dev fd0, sector 0
 [ 35.992049] end_request: I/O error, dev fd0, sector 0
Date: Sat Mar 20 17:34:46 2010
DistroRelease: Ubuntu 10.04
DkmsStatus: Error: [Errno 2] Bestand of map bestaat niet
ExecutablePath: /usr/bin/Xorg
InstallationMedia: Ubuntu 10.04 "Lucid Lynx" - Beta i386 (20100318)
MachineType: HP Pavilion 06 DF168A-ABH T170.
Package: xserver-xorg-core 2:1.7.5-1ubuntu3
ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.32-16-generic root=UUID=1ed36f90-6dd8-4916-8da8-acd31abccb32 ro quiet splash
ProcCmdline: /usr/bin/X :1 -br -verbose -auth /var/run/gdm/auth-for-gdm-GncyXg/database -nolisten tcp
ProcEnviron:
 LANG=nl_NL.UTF-8
 PATH=(custom, no user)
ProcVersionSignature: Ubuntu 2.6.32-16.25-generic
Signal: 6
SourcePackage: xorg-server
StacktraceTop:
 __kernel_vsyscall ()
 raise () from /lib/tls/i686/cmov/libc.so.6
 abort () from /lib/tls/i686/cmov/libc.so.6
 ?? () from /lib/tls/i686/cmov/libc.so.6
 ?? () from /lib/tls/i686/cmov/libc.so.6
Title: Xorg assert failure: *** glibc detected *** /usr/bin/X: realloc(): invalid pointer: 0x096a6dd0 ***
Uname: Linux 2.6.32-16-generic i686
UserGroups:

dmi.bios.date: 07/16/2003
dmi.bios.vendor: Phoenix Technologies, LTD
dmi.bios.version: 3.23
dmi.board.name: MS-6577
dmi.board.vendor: MICRO-STAR INTERNATIONAL CO., LTD
dmi.board.version: 030
dmi.chassis.type: 3
dmi.modalias: dmi:bvnPhoenixTechnologies,LTD:bvr3.23:bd07/16/2003:svnHPPavilion06:pnDF168A-ABHT170.:pvr03Y0211RE101XENO4:rvnMICRO-STARINTERNATIONALCO.,LTD:rnMS-6577:rvr030:cvn:ct3:cvr:
dmi.product.name: DF168A-ABH T170.
dmi.product.version: 03Y0211RE101XENO4
dmi.sys.vendor: HP Pavilion 06
glxinfo: Error: [Errno 2] Bestand of map bestaat niet
system:
 distro: Ubuntu
 codename: lucid
 architecture: i686
 kernel: 2.6.32-16-generic