I have had that happen on a few different laptops I have setup with Slackware12.1 recently, the fix varied depending on the hardware.
to your lilo.conf or (grub) menu.lst file.
(This worked on an Acer Centrino Laptop)
for a Dell laptop I setup recently, I had to install vbetool
and then add the following to /etc/acpi/acpi_handler.sh
# Default acpi script that takes an entry for all actions
*** acpi_handler-orig.sh 2006-09-20 16:06:35.000000000 -0400
--- acpi_handler.sh 2006-09-20 16:16:58.000000000 -0400
*** 5,10 ****
--- 5,13 ----
case "$1" in
/usr/local/bin/vbetool dpms on
case "$2" in
power) /sbin/init 0
*) logger "ACPI action $2 is not defined"
logger "ACPI group $1 / action $2 is not defined"
This worked on another Dell Laptop after installing vbetool.
As Root, edit /etc/X11/xorg.conf, then add to Section "Device"
Option "VBERestore" "true"
You could also try installing suspend
I remember I had some success with one of the systems using that (can't remember which system it was though).
Give one (or all) of these methods a try to see which method works on your hardware.
Hope this helps