I have come across a little glitch that is giving me quite a headache...

I have created a Movie clip that contains an intro animation that contains quite a bit of vector art and 2 JPEG images. Then I inserted this movie clip from my library onto the first frame in the scene. This works beautifully when viewed at "full screen" UNTIL I try to add content to the second frame of the scene... then the JPEG images appear VERY jagged.

Any ideas on what may cause this, how to fix it or prevent it in the future? Thank you in advance for any reply!