I can at least verify what Tanya is seeing as I see it also. The infowindow flickers as you move the cursor slightly in the direction of the infowindow itself. If you move the mouse in any other direction from the graphic, the infowindow will disappear (as expected).
In another situation, I am using a more complex InfoSymbol and it behaves much better. The cursor will flicker if moved slightly in the direction of the infoSymbol, but at least the popup itself will disappear and not flicker.
Carmen