Have you ever had the same window open for more than 30 minutes/one hour open ? Cause mine passed the checkboard test (20 minutes) and the migration assistant window stayed on my screen after one hour ... I really hope your screen are Indeed flawless but so far i haven't seen one ... Your use just have not cause IR so far but somewhere down the road it will most likely happen ... That's why some people thinks they don't have IR ... They just haven't done anything to cause it :/
Don't get mad just because your screen has IR. That's exactly what's going on here.