I have an animation I've exported from Flash Pro CS6 as a MOV file with an alpha channel (ignore stage), and I want to do some editing in AE CS6. When I go to import the MOV as Strait-Unmatted, I do get a transparent background, however when I scrub the playhead with transparency grid toggled, a black background appears behind my animation.

I've tried a number of methods found here and elsewhere on the web including keying out black with luma key, but results were undesirable. Is there a way to get rid of the black behind my animation in AE without effecting the rest of my animation? Or is there an export setting I'm missing in Flash Pro?