I had a few problems with power management too, though they were different. Basically I just force ACPI on so that I can use the power management functions -- SuSE detected APM but I know my computer had ACPI.
THE INSTRUCTIONS BELOW ONLY WORK FOR THE GRUB BOOT LOADER!!
Log on as root and edit the /boot/grub/menu.lst file so that menu entry that boots Linux has "apm=off acpi=force" in the kernel string. See mine below:
kernel (hd0,3)/boot/vmlinuz root=/dev/hda4 vga=0x342 splash=silent apm=off acpi=force desktop resume=/dev/hda3 showopts
Then reboot. ACPI should now be active and all the power management stuff should work. To configure it use YaST. You're screensaver should work now too.
there must be some similar thing for the LILO boot loader but since I dont use it I dont really know how to configure it.