Rust Black Screen

Hello today i buy Rust on steam but i have a problem after playing 5 minutes my monitor goes off with a message no hdmi input detected its only happens with rust game i try ctrl+alt+del but nothing anyway i hear the game sound but nothing happens and i have to restart manual my computer, all other games runs fine, any help i would apreciate it thanks.

My pc specs

Intel i7
8 gb ddr3
Nvidia gts 240
Windows 8.1 Pro