IMac is shutting down when it attempts to sleep with 'hibernate image' error

Question

Our iMac is shutting down when it attempts to sleep.  This started following a Yosemite security update, though of course it is difficult to determine for sure that that was the cause.
In the console, the following message occurs before every shut down:
kernel[0]: Failed to get hibernate image filename
Suggestions?  Does someone perhaps know what exactly the hibernate image is (we have a tiled screensaver that shows an iPhoto album -- could it be that one of those files is corrupt?) so that I can attempt to change it to see if that fixes the problem?
Thanks!
System:  iMac  (21.5-inch, Mid 2011), OS X 10.10.2
Already tried:
I reset the SMC by following Apple's instructions for this computer (turn off, unplug, wait, replug, wait, turn on)

Answer 1

More information:
1. It looks like the crash/shut down is happening when the display tries to sleep (timing is 15 min after the beginning of automatic sleep).
2. When sleep is first initiated, I am seeing this in the console (not normal?):
2015-03-25 9:22:05.987 AM ScreenSaverEngine[485]: Preflight for plugin com.apple.ILPhotosPlugin failed, so it will not load. Error Domain=NSCocoaErrorDomain Code=3587 "The bundle “iLMBPhotosPlugin” couldn’t be loaded because it is damaged or missing necessary resources." (dlopen_preflight(/Library/Application Support/iLifeMediaBrowser/Plug-Ins/iLMBPhotosPlugin.ilmbplugin/Contents/MacOS/i LMBPhotosPlugin): Library not loaded: /System/Library/PrivateFrameworks/PhotoLibraryPrivate.framework/Versions/A/Phot oLibraryPrivate
  Referenced from: /Library/Application Support/iLifeMediaBrowser/Plug-Ins/iLMBPhotosPlugin.ilmbplugin/Contents/MacOS/i LMBPhotosPlugin
  Reason: image not found) UserInfo=0x7fed83841320 {NSLocalizedFailureReason=The bundle is damaged or missing necessary resources., NSLocalizedRecoverySuggestion=Try reinstalling the bundle., NSFilePath=/Library/Application Support/iLifeMediaBrowser/Plug-Ins/iLMBPhotosPlugin.ilmbplugin/Contents/MacOS/i LMBPhotosPlugin, NSDebugDescription=dlopen_preflight(/Library/Application Support/iLifeMediaBrowser/Plug-Ins/iLMBPhotosPlugin.ilmbplugin/Contents/MacOS/i LMBPhotosPlugin): Library not loaded: /System/Library/PrivateFrameworks/PhotoLibraryPrivate.framework/Versions/A/Phot oLibraryPrivate
  Referenced from: /Library/Application Support/iLifeMediaBrowser/Plug-Ins/iLMBPhotosPlugin.ilmbplugin/Contents/MacOS/i LMBPhotosPlugin
  Reason: image not found, NSBundlePath=/Library/Application Support/iLifeMediaBrowser/Plug-Ins/iLMBPhotosPlugin.ilmbplugin, NSLocalizedDescription=The bundle “iLMBPhotosPlugin” couldn’t be loaded because it is damaged or missing necessary resources.}
The iLMBPhotosPlugin file does exist:
ls -al "/Library/Application Support/iLifeMediaBrowser/Plug-Ins/iLMBPhotosPlugin.ilmbplugin/Contents/MacOS/"
total 80
drwxr-xr-x  3 root  wheel    102 30 Jan 07:46 .
drwxr-xr-x  7 root  wheel    238 30 Jan 07:46 ..
-rwxr-xr-x  1 root  wheel  99840 29 Sep 01:41 iLMBPhotosPlugin
The Library PhotoLibraryPrivate.framework/Versions/A/PhotoLibraryPrivate does not (there is no directory called /System/Library/PrivateFrameworks/PhotoLibraryPrivate.framework)
sudo ls -ald "/System/Library/PrivateFrameworks/Photo"*
drwxr-xr-x  3 root  wheel  102 11 Sep  2014 /System/Library/PrivateFrameworks/PhotoLibrary.framework