shutdown or acpi problem

I have a kernel/world from r274273 sources, which is exhibiting a new
issue on my old laptop.  Neither 'shutdown -p now' nor 'shutdown -r now'
work.  I get to the end of shutdown and see for example

All buffers synced
Uptime: 4h23m15s

and then the laptop just sits there.  It does not power off with
the -p option nor does it reboot with the -r.  Has anyone else
seen this behavior?

-- 
Steve