I experience exactly the same problem described in another post: my Samsung Ativ Pro PC regularly fails to hibernate and sometimes even sleep after upgrading to Win 8.1. The answer in the earlier post (disabling 'Wake on ...' settings in the network adapter properties) did not solve the problem for me. I've tried quite a few other suggestions, including deleting my hibernation file and regenerating it, searching for software wake-up calls and checking in Device Manager that none of the drivers was 'allowed to wake this device'. Nothing works consistently sofar. Last night my battery drained completely, because the laptop must have woken itself after I put to sleep last night (failing to get it to hibernate in the first place). Any other suggestions would be welcome!
Thanks in advance, Wim