Odds are what you are experiencing is when it checks for updates and parts. It will become unresponsive and give no feedback. If you try and do something your system will think it has crashed and ask if you want to force it closed. If you force it closed you will corrupt the database. Once it is corrupted you will have to clear the hidden user directory and start over. Once you have cleared the directory and tried starting Fritzing again you need to wait until it becomes responsive again and NEVER force it closed even if it unresponsive for a very very long time.
EDIT: it turns out that Peter edited his answer and added the same info but I didn’t see it until after I wrote mine.