I'm trying to get our PCs to hibernate when idling, but am having trouble. Via Group Policy, I have configured the power settings, and everything looks fine however the PCs never actually hibernate. I figured that another Policy was preventing them from doing this, so set to looking for it. I found a Policy which set HKU\Default\Control Panel\Powercfg\current policy, so applied that to my test computer (which has always hibernated) and sure enough it stopped hibernating. I created a modified version of that Policy which had that line removed, applied that to my test PC and hibernation started again. So, I applied the modified Policy to all my other computers, but they're still not hibernating. I've been right through all the Location and User Policies and can't find any others which govern power settings; there's nothing in the BIOS either way about hibernation settings.

What am I missing?!