Hi,
I've reviewed the other contributors and am happy to defer to their expertise.
I'm puzzled that liveupdate can wake up a system from hibernation on its own ... seems wrong on so many levels.
Microsoft (mobo manfucturers too) has had a legion of problems getting systems to go nighty night and wake up properly. Some won't go to sleep at all ... others won't wake up shy of a defribrilator jolt.
There's plenty of discussion about either situation on the forums. An obvious issue to exclude is your motherboard settings - as in, check to make sure your LAN (NIC card) doesn't wake your system up. There are reasons for having it - if they apply to you then I guess, let it alone.
Other forums suggest getting the very latest bios / chip drivers for your motherboard and CPU etc. I know this sorted out similar problems with one of my systems ... did zip for another. HP systems are known to have the problem you describe ... mobo settings??
This link refers to an HP notebook. It describes the fix in detail and may help here ... similar principles.
This is a real stretch - have you checked your scheduled tasks to see if there is anything unwanted happening? If you are using XP, go control panel - scheduled task. It will show you what tasks are set to run and when. For Vista: Control Panel \ System and Maintenance\Administrative Tools\Task Scheduler ... take a look around.
HTH