Render crash randomly

I’m a beginner on Blender, actually I’m working on a library of my materials sets and some shared sets from Blenderswap.

When I launch a render it crash randomly and show a huge RAM utilisation value which isn’t normal.
Why ist it happening and how can I solve this problem please?

By the way my config :
Windows 8.1 64 bits pro
MSI Z87 GD65 Gaming
i7 4770K 4,2Ghz
16Go G.skill Trident X 2400Mhz CL10 (2x8)
MSI GTX 780 Ti 3Go