When you are Hibernating, it is effectively shutting off the PC or Laptop. You mean, the system is crashing right in the middle of a Hibernation operation? Need some clarification here, Hibernation saves ALL of your open processes and files and then shuts down your puter, when you open it back up, it goes right back to where you were before you Hibernated. But Hibernation is a complete shut-off, it is not a "low power" mode. If you are talking about Standby, well, Standby has never worked right form Windows since Windows ME. But Hibernation works well. So, are you telling your system to Hibernate when the lid is closed? That mans it is powering OFF. If you are telling it to Stand-By when the lid is closed, that's a Standby mode. Standby mode has always been unstable in Windows systems, but should work right if you have all of the best Drivers installed for your Chipset.
I have Three Windows 8 Installs and they all Hibernate fine. Depending on if you upgraded your Laptop to Win 8 or bought it that way, you might have to download Windows 8 Drivers for your Power Block, AHCI, etc. Install the current version of Aida64, and find your Motherboard make, then look it up and find if there are any new Power drivers for it. It's a Program like Speccy, which reads your system and tells you what you have under the hood, but unlike Speccy, it actually identifies each piece of Hardware, including if it is not installed properly on the OS, this way you can look up the drivers and find the right one.