help with repeatable display anomaly

If I have iTunes running and close its window so it is running in the background and If I then start Safari and after done with it shut down Safari a white rectangular area that is exact size and shape of the closed iTunes window appears on the desktop. The only way of getting it to go away is to reopen the iTunes window and close it again. This happens a lot as I keep iTunes running so my Apple TV can stream, but I close the iTunes window as I don't need it open. So every time that I open Safari and get on to the Internet, I see the problem when I quit Safari. Possible unique things are I run multi user and I also have a custom display profile. I tried going to a solid desktop back ground but it didn't help. My system basics are listed below. Any ideas? I could not find anything using search even close.