I have a similar problem as reported in Thread 'Cloning Slide with Autoshape Arc' started on 07-25-2006, 6:25 PM.. In my case the autoshape RectangularCallout causes the same problems than the autoshape arc in the thread mentioned above.
Cloning a Powerpoint 2000 presentation that contains an autoshape of type RectangularCallout leads to an empty slide when opened in Powerpoint 2000. Strange to say the same cloned file opened with Powerpoint 2003 or 2007 shows all shapes properly including the autoshape RectangularCallout.
Do I remove the autoshape from the source slide cloning works fine and the presentation is opened by Powerpoint 2000 properly.
Unfortunately my client works with 2000 :-(
Looking forward to your advice
PS: I am working with aspose.slides version 2.7.8. A test switch to the newest version has shown the same problems.