Alpha Problem with Lens Flare Effect when imported to Final Cut!!

I've just output a lower 3rd animation from AE as a QT file, RGB+Alpha, Unmatted, Animation compression. It includes a little lens flare animation for the text that when, and only when, it appears on screen I get a black background covering my final cut footage. When the flare fades out my footage is then visible again with the lower 3rd graphic. I've imported the footage into AE to check my mode settings to make sure they work and it looks great, so it must be the way I'm exporting? I'm super exhausted right now, so my apologies if this is a little inarticulate. If anyone out there can help I'd be forever in your debt!

Thanks,
J

JB