Short of a long trouble-shooting session was that a set of jpegs were causing an error on loading and shutting Vegas 5 down. The files were given to me by the client, and as soon as I set them to 16-bit or converted to PhotoShop PSD, the files loaded fine and the crashing stopped.
Question is, why would Vegas recognize/allow/render a file type that causes a crash when the media is being retrieved upon loading? No warnings...nothing...you see the file in the preview window. Put it on the timeline just fine. Render it. No problem. Save & try to re-open it, and you get nothing but an "OK" button and the program closes. I would think it wouldn't allow it to begin with, but it does.