Hey neoarcadia, sorry for the late reply. I assume that since you didn't re-post here, you solved your problem? If not, here's a suggestion to try.
Create a new scene. Import your old scene into the new scene. Create new cameras and render.
I know, it's a weird solution and doesn't give a technical answer. But I've also had those problems where the scene just wouldn't render. I did what I said to try and it worked.
If you've already solved it, we would appreciate it if you could post your solution here for anybody else with the same issues.
Thanks.
Dave Baer
Professor of Digital Arts
Digital Media Arts College
Boca Raton, Florida
dbaer@dmac.edu