The Short Version: The process quits with an error if the display sleeps. Disabling the display sleep option works around the problem.
My wife spent hours working on an iPhoto Slideshow but ran into a problem. When she tried to export to iDVD the export process crashed.
I attempted to export the Slideshow to an MP4 file, thinking that perhaps it was a problem with the integration between iPhoto and iDVD. Somewhere in the process it failed and reported an error of “OSStatus error -9459”.
Despite the fact that it crashed I did have an error code to research at that point. I quickly hit upon one solution in a Mac Forums post offered by user 6string. The suggestion was simple: change the display sleep delay to “Never”.
My wife’s laptop wasn’t set to sleep but the display was. I made the change and fired off another export process. Once I know it’s successfully completed I’ll add an update to this post.