Problem with monitor refresh rate

I have a benq gl2580 ,which 5 months ago, I overclocked to 75hz and everything works nicely. But recently i'm noticing some problems. When i first start my laptop (note: i have a lenovo y520 connected to the benq with hdmi, and only the benq is set to work as my main monitor) the screen is grey-ish and when i check windows settings it's on 60hz, after a restart everything is fixed. It's really annoying to have to restart every time i start the laptop
P.S I've played with throttlestop which might cause my problem!