How can I avoid grey/white checkerboard pattern when tweening?

[MediaGuy]

When I "tween" from one frame to another, IR creates faded images, of course, but at least one of those images has a very obvious grey/white checkerboard pattern. This is the same pattern you see in photoshop when you are looking at a transparent layer without the background showing.

How can I do tweening without having this pattern show up?

Any and all help apprecaited.