The entry of data and running the analysis work fine, but when the project is saved, the window freezes. There is no Save dialog. ConCrete can only be ended through Task Manager.
Solution
The Main ConCrete window is maximized. The Save dialog has been opened behind the Main window. The Save dialog is not recognized by Windows as an other dialog, but rather as a part of the Main window. Consequently, the Main window freezes when the Save dialog is open, and it is not possible to bring the dialog in front by using ALT+TAB. When the Main Window is not maximized, the Save dialog will become visible and the project can be saved.