Go to adobe.com and update your Flash player. I think the little white window is the dialog that asks you update your player, no idea why it disappears.
I've updated flash and made sure that pop-up are okay from this site, but I still get nothing but a blank, black screen. This is a fairly new computer. With my old computer, I could view the flash teases no problem. On this one, for the life of me, I can't make them work. The flash player seems to be working ok, because I have watched other flash content. Does anyone have any other ideas?