Drag and drop not working on Mac

By testing my extension in a Mac I noticed that drag and drop doesn't work as expected. Therefore I have created a new simple extension with only one list and a simple data provider:

  [Bindable]

  public var aData:ArrayCollection = new ArrayCollection(['one','two','three','four']);

            <s:List dataProvider="{aData}" dragEnabled="true" dropEnabled="true" dragMoveEnabled="true"> </s:List>

this should allow the user to reorder the items in the list by dragging them.

It works fine in Windows as extension for Photoshop CS6 and also in Mac as AIR application but it doesn't works as Photoshop CS6 extension in Mac (Lion); I can neither see the drop line between items.

Is this a known problem and which is the workaround ?

Thanks