I made 2 presentations: Danube River Cruise 1 and Danube River Cruise 2.
I saved each presentation under a different name.
I proceeded to rearrange the slide order using slide sorter.
Suddenly, I lost about 20% of all slides; they became 90% black (images
What baffles me is that both #1 and #2 and the saved copies of each suffered
the same phenomenon.