all of these workarrounds don´t work.
I installed 3 Mac Minis, and all of them got the same problem.
I tried as Guestuser - the same.
Iv´e tried too to redet the Index from the NAS, but can not change it in terminal.
Iv ´e tried to reset the Index by the Spotlight-Pref (add to private and so on...) no effect.
It continues to work on my computer in Mavericks and Yosemite.
I suspect there is third-party software installed which may interfere. Try creating a new user on your computer and see if you see the same problem there.
Like i told, i tried as another (fresh) User (Guest) - the same problem.