Using ProjectLibre 1.7, both 32 bit and 64 bit version on Windows 10 Updated to 1703. It can open the project but I can't make any changes to it. As soon as I click Save after making a change, projectlibre gracefully exits as if you have clicked the close button. I tried opening a new Project, typing one task and saving it with the same result. Even going for Print PDF button, gracefully exits. You just cannot work with it.
Can you please specify the format of the file you opened? (Is it .mpp?)
Is it possible to upload the file?
Can you please try the Save as?
Please pay close attention what is in "Files of type:", when I had "All Files" it saved an XML file with the .POD extension, which needed renaming, otherwise it could not be opened again.
(As Windows by default hides the known file extensions this can be a difficult task on some computers.)