When I print my slides or convert them to a PDF-file a dark square appears at the bottom of the picture!

There is a gradient at the bottom of the second slides. If you get this problem just try to remove it from your presentation. To remove the gradient please do the following steps:

1. Open your presentation
2. Select from main menu “View -> Master -> Slide Master”
3. Click once on the bottom of the slide to select the gradient
4. Press Delete or Del key to delete the gradient
5. Close master view and save the presentation.