Error: an unnamed file contains an incorrect path?

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

Error: an unnamed file  contains an incorrect path

It means that there is a small problem 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  can be found under Setup:

Temporary files

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