I'm new to Vegas Video 2.0g, but I just
tried this on a project:

1. Create a generated text event on a video
track.

2. Use the event motion button on the event
to open the motion/crop/pan/zoom editor.

3. Set the initial position of the text event.

4. Add a keyframe at the appropriate
ending time of the event.

5. On that new keyframe, re-adjust the text
event's position.

Using the above technique I was able to make
text scroll smoothly for credits. I found that
I had to be careful in the amount of text
that I used and the font size to keep it from
clipping within the frame window.

Not the most elegant, but it worked for me.