If you copy and paste you may have picked an illegal character and placed it in the noted of one of the people that causes the crash. Illegal characters can do strange things
Is there common text strings in each person's notes?
If it were me I would copy each of the notes to a word processor. You could also print the note either to paper or to a PDF file then you could then copy and paste it back.
Once I had saved the text, I would delete each note, compact, close and restart FTM. I may compact again. I would then reload the text to each note. If you go the PDF route you may want to run the text through text document.
If this does not work you may have to delete the offending people and recreate them. Do forget to disconnect them from the tree before deleting them. I would use the same technique to preserve the data.