I recently found out about a external render engine called Kerkythea.
When I download it, it gives me a blender application.
When I open the blender application it brings me to blender 2.48.
So I open a project I was working on in the blender 2.48 application.
And it loads up fine.
When I switch it to render with Kerkythea and hit render it just shows a black screen in the render box.
The same thing happens with Yafray.
I have a Intel Mac OS X. With 1 GB of RAM and running Snow Leopard.