All my images dissapeared. What happened?
Try using the 'Show all' command, it is very easy to select an empty container. MediaPro displays the contents of selected containers and in this case there wouldn't be anything to display.
When I play one Audio or Movie file the whole catalog starts playing. How do I stop it?
This is called playlist mode which is useful for catalogs of playable media. To turn it off go to the playlist icon, which is on the menu bar after the window menu, and deselect it.