I have been attempting to "export" a video or "Make Movie" in Vegas 6, but the thing says it's working and then makes about 70 percent of the movie and then stops. The avi file it spits out is incomplete and lacks audio. WTF?
Use File/RenderAs and export in another format. See if the other encoded format completes the video and it has audio. If yes, then you are hitting an encoder bug.
Vegas doesn't handle memory well while rendering large numbers of large still images. Unless you're zooming from the whole image far in to just a small portion, you may want to consider resizing some of the image files first. Generally there's no reason to have the images larger than the output frame size unless you are zooming in.
This is an old, frustrating problem with VMS -- it has been discussed many times in the past. The last thread that I recall is here. In a nutshell, you need to resize your pics down to HD dimensions or less to prevent VMS memory management from getting confused.
I seem to remember hearing somewhere that this is fixed in the new release (VMS 8) but I can't say for sure if it is or not.
I've actually just completed a 10 minute DVD which uses a combination of about 100 high res photos, avi and mpg. The photos are up to 2.3GB with a maximum dimension of 2300. Various pans and zooms. It renders without problems. I'm using 8.0b.