Have you tried;
interObj.mouseEnabled = false
I'm using a DropDownList and it doesn't have the "interObj" or "InteractiveObject" properties.
I'm working with the Flex SDK 4.0
I'm not sure what you're trying to do, but in general, Flex components don't
behave well when parented by plain Sprites.
I changed the Sprite to a BorderContainer, same result.
When the mouse goes out of the BorderContainer, it's hidden, I need to prevent this when the DropDownList that is inside the BorderContainer is open and the mouse is over the list.
I think you'll need to post a simple test case.