SUSE Linux Enterprise Server 11
SUSE Linux Enterprise Desktop 11
The problem can occur with or without a Support Pack installed.

During a shutdown or reboot the system will shutdown appropriately but at the point where it should power off or begin the reboot it will hang.  The power must be manually turned off or cycled to boot the system back up.

The kernel has a "reboot" parameter that will generally fix the problem.  Each of the options can be tested on bootup of the system by adding the parameter to the "Boot Options" in the GRUB menu.  Here is a list of all the options:

warm =  Don’t set the cold reboot flag
cold = Set the cold reboot flag
bios = Reboot by jumping through the BIOS (only for X86_32)
smp = Reboot by executing reset on BSP or other CPU (only for X86_32)
triple = Force a triple fault (init)
kbd = Use the keyboard controller. cold reset (this is the default)
acpi = Use the RESET_REG in the FADT
efi = Use efi reset_system runtime service
pci = Use the so-called “PCI reset register”, CF9
force = Avoid anything that could hang.

Most of the time the problem can be fixed by using one of the following two parameters:

reboot=bios
reboot=acpi

Try these first then move on to the others if needed.

Each time you boot up with a new parameter you can verify that it was really used in the kernel load line by entering this command:

cat /proc/cmdline

This will return the options the kernel was loaded with and would look something like this:

root=/dev/disk/by-id/ata-WDC_WD3200BEKT-75KA9T0_WD-WXA1A80E1055-part5 resume=/dev/disk/by-id/ata-WDC_WD3200BEKT-75KA9T0_WD-WXA1A80E1055-part3 splash=silent vga=0x314 reboot=bios

Just look for the "reboot=" parameter and make sure it is appropriate.

Once the parameter is found that works for the system it can be added to the grub menu so it will be included on every boot.  Here are the steps:

Load YaST and take the selection for System--> Boot Loader.

Highlight the default selection (the one with the check mark in the first column) and click the Edit button.

In the entry titled "Optional Kernel Command Line Parameter"  add your new parameter to the end of the line.  Click OK to save the new setting.  Back on the Boot Loader Settings window click OK again and reboot the system to test it out.

The reboot= options are all listed in the following file (if you have the kernel source installed):

/usr/src/linux/arch/x86/kernel/reboot.c

In addition, you can see in this file that there are specific settings for this parameter applied for certain models of Dell, HP, and others to work around BIOS issues.  Of course, the exceptions are not complete so manually changing this parameter will be required for some systems.