We found strange behavior in OSX 10.7.2 where when we try tun /System/Library/Frameworks/ScreenSaver.framework/Resources/ScreenSaverEngine.app/Contents/MacOS/ScreenSaverEngine
the screen saver just doesn't start… nada.
So we have put in a test 1 second after the saver starts to check that it is indeed running, and if not we try running it a different way:
open /System/Library/Frameworks/ScreenSaver.framework/Resources/ScreenSaverEngine.app
and also notify the user. A restart or even running the saver manually seems to "fix" the issue.