Windows 7 fails to hibernate

Althrought everything worked fine for about 6 months. Now computer fails to hibernate. It success for about 1/3 times and fails 2/3 times.

There are two different scenarios of failures which occurs randomly:
1. During hibernation screen goes of, HDD is working for few seconds and after that HDD stops working but PC is still powered on. After powering down by pressing power button for 3 sec. and powering on again Windows starts like a normal clean start, like it was just shutted down instead of hibernated.
2. This one is more strange. During hibernation screen goes off, HDD is working for few sec. and finally goes STANDBY instead of hibernate.

In summary: in 1/3 times goes hibernate, 1/3 hangs during hibernation, 1/3 goes standby instead of hibernation.

Things done to resolve problem:
1. Disable/enable hibernation using powercfg -h tool
2. Change hibernation file size to 100% of amount of RAM (powercfg -h size 100)
3. Run deep CHKDSK during system boot
4. Run deep antyvirus scan using Avast 4.8 (in boot mode)
5. Check system logs. All (maybe) usable information I found was - Application and Services Log -> Microsoft -> Windows -> Kernel-Power -> Thermal -> Working of processor 0 (or 1) was reduced by process different than kernel power manager (ID:91).
6. Check running processes to find any strange or suspicious. Didn't find anything suspisious

Nothing specific has changed to my computer software/hardware
Hardware is: Fujitsu Siemens Esprimo V5545.

Jonathan_King said:

First, try opening a command prompt and typing sfc /scannow. This scans for bad system files, and repairs them if necessary.

If that does not work, perhaps a Repair Install will. Don't worry, your programs and files will be untouched,

I've tried sfc command, it took about 10-15 minutes. After finished told me that found some errors but couldn't repair them all and details are in log file. This log file is HUGE (about 7KB of plain text!!!). I don't know what should I look for in it. However it doesn't solve my problem.

For system restore is rather too late because problem occured first 2-3 weeks ago.

I could try Repair Installation but as far as I know Microsoft.... it won't work. Microsoft Installer don't really fix inproper entries in registry, it only adds missing ones

I can post a log file from sfc.exe if someone know how to read it.

SOLUTION FOUND !!!

I finally found the cause of this problem. It was so primitive that I didn't come out earlier on this.
I've noticed that this issue almost never happens in my work and almost always happen in my home. What is a difference between my home and work ? Answer is - network location. Of course "network location" known from Windows Vista & 7 has nothing to do with it - I'm talking about physical network in which computer is currently connected to. In wireless network card configuration I found some options typicall for M$ Windows which are (translated from polish to english so may not be exact as in english version of Windows):
a) Allow this computer to turn of this device to preserve power consumption
b) Allow this device to resume computer from standby

Option a) MUST be enabled for computer to be able to hibernate/standby because ALL devices must be compatible to EnergyStar standard to allow computer to hibernate

althrough....

Option b) allows computer to wake up via "Wake Up on LAN" or Magic Packet (as some call it).

Somehow I had to enable option b) by coincidence so my computer couldn't hibernate because some wake-up packets were flown through network (from router i.e.). That's why in my work this issue had almost never happen where in home in some reasons happened almost every time because of my router or other device in network was sending WOL signals each second.

Problem was very strange - solution very simple ----- as usual ;-)

Thanks to all of you folks helping me try to solve this problem and I hope that this thread will help someone with common problem in future.