Hi,
This is a premultiplication error common when looking at an animation with a soft alpha channel in an editing system.
When you render the animation, in the output module, obviously you will be setting the “Channels” to RGB+Alpha. Under this, set color to “Straight – Unmatted”
The resulting animation will look horrible when viewed in Quicktime, but will mask properly in the Avid.
Hope this helps.
Lars