Hi Maurice,
reading your post above, what I understand is that your system shutdown process completed correctly, in fact "Power off" is the last message you can see from a whole shutdown process.
By "However it failed to shutdown" did you mean that the machine doesn't turn off ?
If so, this could be something specifically related to your Hardware/BIOS/ACPI ...
can you provide some more info about your system ?
did you check for an eventually available BIOS update ?
can you post your file /boot/grub/menu.lst (or at least the kernel parameters you are actually using) ?
AS
1---Correct
2---Yes
3---Details of my machine are in my sig. I can't think of any more that might be relevant.
4---Here' my menu.lst
timeout 1
color black/cyan yellow/cyan
gfxmenu (hd0,3)/boot/gfxmenu
default 0
title linux
kernel (hd0,3)/boot/vmlinuz BOOT_IMAGE=linux root=LABEL=PcLinuxOS10 vmalloc=256M splash=silent vga=788
initrd (hd0,3)/boot/initrd.img
title linux-nonfb
kernel (hd0,3)/boot/vmlinuz BOOT_IMAGE=linux-nonfb root=LABEL=PcLinuxOS10 vmalloc=256M
initrd (hd0,3)/boot/initrd.img
title failsafe
kernel (hd0,3)/boot/vmlinuz BOOT_IMAGE=failsafe root=LABEL=PcLinuxOS10 failsafe vmalloc=256M
initrd (hd0,3)/boot/initrd.img
title windows
root (hd0,0)
makeactive
chainloader +1
title PCLinuxOS (PCLinuxOS)
root (hd0,1)
configfile /boot/grub/menu.lst
title 2.6.33.5-pclos1.bfs
kernel (hd0,3)/boot/vmlinuz-2.6.33.5-pclos1.bfs BOOT_IMAGE=2.6.33.5-pclos1.bfs root=LABEL=PcLinuxOS10 vmalloc=256M splash=silent vga=788
initrd (hd0,3)/boot/initrd-2.6.33.5-pclos1.bfs.img
title 2.6.38.8-pclos1.pae.bfs
kernel (hd0,3)/boot/vmlinuz-2.6.38.8-pclos1.pae.bfs BOOT_IMAGE=2.6.38.8-pclos1.pae.bfs root=LABEL=PcLinuxOS10 vmalloc=256M splash=silent vga=788
initrd (hd0,3)/boot/initrd-2.6.38.8-pclos1.pae.bfs.img