the backlight is flashing

the backlight is flashing when the login screen (gdm) is launched. it continues until switching to a console, waiting a while and switching back.

ProblemType: Bug
Architecture: i386
Date: Fri Oct 23 08:01:22 2009
DistroRelease: Ubuntu 9.10
ExecutablePath: /usr/bin/Xorg
MachineType: MICRO-STAR INTERNATIONAL CO., LTD U-100
Package: xserver-xorg-core 2:1.6.4-2ubuntu3
ProcCmdLine: BOOT_IMAGE=/vmlinuz-2.6.31-14-generic root=/dev/mapper/hostname-root ro quiet
ProcEnviron:
 LANG=en_US.UTF-8
 PATH=(custom, no user)
ProcVersionSignature: Ubuntu 2.6.31-14.48-generic
RelatedPackageVersions:
 xserver-xorg 1:7.4+3ubuntu7
 libgl1-mesa-glx 7.6.1~git20091017.3594b53c-0ubuntu0~xup~1
 libdrm2 2.4.14-1ubuntu1
 xserver-xorg-video-intel 2:2.9.0-1ubuntu2
 xserver-xorg-video-ati 1:6.12.99+git20090929.7968e1fb-0ubuntu1
SourcePackage: xorg-server
Tags: ubuntu-unr
Uname: Linux 2.6.31-14-generic i686
XorgConf: Error: [Errno 2] No such file or directory: '/etc/X11/xorg.conf'
XsessionErrors:
 (gnome-settings-daemon:2066): GLib-CRITICAL **: g_propagate_error: assertion `src != NULL' failed
 (gnome-settings-daemon:2066): GLib-CRITICAL **: g_propagate_error: assertion `src != NULL' failed
 (nautilus:2100): Eel-CRITICAL **: eel_preferences_get_boolean: assertion `preferences_is_initialized ()' failed
 (polkit-gnome-authentication-agent-1:2108): GLib-CRITICAL **: g_once_init_leave: assertion `initialization_value != 0' failed
 (nautilus:2211): Eel-CRITICAL **: eel_preferences_get_boolean: assertion `preferences_is_initialized ()' failed
dmi.bios.date: 12/03/2008
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 4.6.3
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: U-100
dmi.board.vendor: MICRO-STAR INTERNATIONAL CO., LTD
dmi.board.version: Ver.001
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: MICRO-STAR INTERNATIONAL CO., LTD
dmi.chassis.version: Ver.001
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr4.6.3:bd12/03/2008:svnMICRO-STARINTERNATIONALCO.,LTD:pnU-100:pvrVer.001:rvnMICRO-STARINTERNATIONALCO.,LTD:rnU-100:rvrVer.001:cvnMICRO-STARINTERNATIONALCO.,LTD:ct3:cvrVer.001:
dmi.product.name: U-100
dmi.product.version: Ver.001
dmi.sys.vendor: MICRO-STAR INTERNATIONAL CO., LTD
fglrx: Not loaded
system:
 distro: Ubuntu
 architecture: i686kernel: 2.6.31-14-generic