It seems the alpha is not "drawn". Part that should be transparent contain random memory elements.
The clearColor is set with a 0 alpha and I tried different transparent shader.
Am I missing something here ?
The SWF is very simple. A moving circle with no other elements. As you can see in the screenshot below, the transparent part is never redrawn.
This is on Mac 10.8.5 and Unity 4.3.4 with the march release of Scaleform.