Render problem, rendering suddenly stopped

The rendering was working well but suddenly stopped.

So i tried again, then nothing happened in the program. I need to reboot the laptop.

Sometimes 'Out of memory' window pops up, but my labtop has enough memory more than 30GB. 

How can I fix this problem?

(I tried Purge to erase all of the memory in AE.  program that I wanna render is After Effect.

Also I don't thinks the graphic card has some problems, it's enough to render this.

This never happened until last month.)

Thanks.