This can happen sometimes with upgrades. For some reason your user details get removed from the ini file. With the program closed, navigate to the FPS Creator directory and look for a file named "userdetails.ini". Open it with notepad. It should look like this....
[PERSONAL DATA]
YourName=
YourSerialCode=
YourFullPath=C:\Program Files\The Game Creators\FPS Creator
[LOCALIZATION]
language=english
Just put your name and serial code back in (no spaces) and save the file. When you restart FPS Creator, you should be good.
You can make a copy of the "userdetails.ini" file and save it for later when this happens again. Then just copy the backup file to the FPS Creator directory to overwrite the broken one.
Brian.