Error: an unnamed file contains an incorrect path?

If by opening a project in SCIA Engineer, the following message appears:

It means that there is a small probem with the temporary files. 

This message can appear in a student version of SCIA Engineer, but also in the full version.
After deleting the temporary files, the project can be opened again.

The location of the temporary files can be found under Setup:

The folder has to be deleted. This can only be done if SCIA Engineer is completely closed.