Image quality deteriorating

I’ve got a Flash movie into which I have imported a .avi video clip. When the video is imported the extra frames are automatically added to the timeline in order for the video to be viewable.
However, as soon as any extra frames are added the quality of the images on other layers is immediately lessened - making them fussy and rough around the edges.

If anybody has idea how to get round this I would be eternally grateful.

Cheeers.