Rendering will take a very long time - I once needed 6 hours for a shorter high definition movie with plenty of effects.
What theme are you using and what settings?
The "places" theme needs a good network connection.
And the finished movie will need plenty of disk space.
And the finished movie will need plenty of disk space. Have you checked the available space on your disk?
What exactly happens when Aperture fails to render the movie? Are there any diagnostics, error messages in the console window, that relate to Aperture? Does Aperture alway stop at the same image or video clip?
if all fails, you could render your slideshow in two parts and combine the two videos on your DVD.
For what it is worth, I am having similar problems. I'm still working on this and will stay in touch as I succeed or fail with the Export process.
I made a 46.5 min aperture slide show and tried a number of times to Export it so I can burn it to DVD to be viewed on an HDTV, so far with no success! I set computer sleep to 3hrs and let it export over night and the furthest i've gotten is 66% Exported! Why is it taken so long and seem to stop but the activity status goes up ever so slowley???? Im using an iMac 7,1 2.4 GHz with 6GB of memory running 10.8.2 what am I doing wrong???