Need help moving a video though the frame/canvas

Hello all,

First, I am self-teaching through a variety of resources and while I tend to be a quick learner, please be patient if my lingo is confusing.

Ok. So I am working on a montage of current events, video clips of news stories, most without using the audio, but plan on overlapping selected audio clips as the clips and articles move through the frame (perhaps called a canvas). While I have mastered motion (I think), what I cannot seem to get right is getting a video clip that I have changed the perspective (swivel) of to move in a "straight" line across my frame.

I keyframe the distance to object at the begining of the clip and would like the clips to crawl towards (or away) from the viewer as it plays. Unfortunately, I have not figured out how to achieve the desired effect. The video starts off playing (moving through the frame) as it should, but towards the end, its almost as if the track it is on curves towards me and the clip gets stuck until the end halfway in frame instead of continuing on past.

If this made any sense to you and you have the "magic" forumala, I would be very grateful. Also, any constructive criticism about word choice that may help better explain my issue would be welcomed.

Thanks much.