shutdown -p now does not power off the MotherBoard

[Sam Rajarathinam]

I have a X86 Mother board which can be powered off
from software command "shutdown -p now" using FreeBSD
5.1, 5.2 but not with 5.3, 5.4 or 6.1. Unfortunately
the acpi diff between 5.2 and 5.3 is ~50000 lines. I
see the tasks acpi tasks are started properly in 5.3,
5.4 or 6.1. Tried playing with asl file also using
acpidump. I am not sure where to start looking. Any
pointers?
Thanks.
-sam