This only happens on the initial power on. Reboots are fine. Sleep mode couldn't wake up. I hit all manners of keyboard buttons, moved mouse, hit mouse buttons, monitor stopped getting signal (basically what I see when it doesn't work). The keyboard then went into a seizure (Logitech G15) and the lights on my keys were just flashing really fast.
Powered unit down, pulled and replugged displayport cable (tried a couple, including one new one from monoprice) and PC came back on, windows went "resuming windows" and now it's back on.