Vista "Sleep" and "Hibernate" arent working.

Is there a way to go back to the same sleep and hybernate functions that were
in XP.
my laptop dopes not want to work with vista's new advanced sleep and
hibernate functions.
Whenever I try to put the computer to sleep or hibernate the screen goes
black and the HD activity light comes on solid. Within a few seconds the
computer reastarts and I see the HP boot/post screen. Windows then says that
windows was not shut down properly and asks if I want to start windows
normally.
I never had problems using sleep or hibernate in XP so I know its not a
hardware issue. (my laptop is a HP Pavillion ZT3000 Intel Centrino 1.8ghz,
1.25gb ram)
HP does not have any firmware updates available and I have installed the
latest chipset drivers from Intel.

If anyone knows how I can get Sleep working weather its the normal sleep or
vista sleep i would be happy. lifing with Vista is going to be a pain if i
have to completely shut down my notebook 2-3 times a day.