Why does one monitor repeatedly go black on me?

So we got new lenovo computers, and they come with the display port rather than vga. I bought adapters and upon hooking everything up seemed to run fine. One day talking to someone I noticed out the corner of my eye something flash on my monitor. I thought I was going insane because it happened quite a few times always while i was looking away. So i then stared at my computer for about 10 minutes to notice there's a little black line that will hop across my screen. I then replaced the VGA cable aswell as the display port adapter. It seems to work fine, but when i'm away from my computer or doing something else. I notice upon return that everything on my two screens has been moved to one screen as if the monitor in question had shut off. Forcing my split screen into one screen, then turning back on and all my stuff stays on the one monitor. No big deal for me I can just move stuff back, but it seems to happen to every lenovo i'm putting up. Is this a common issue with lenovo? Maybe its just the adapters i bought?