Sounds like the one file that made your machine screen go black is corrupted. I have had this happen to me before in my digitizing software where the software had a "bug" and when the file was saved, it was 'confused' and my sewing machine did not recognize the file...very frustrating indeed. Something could have also happened in the download of the zip file or when you unzipped the file...If you have the alphabet and the other letters are good, I would take another letter with the "good" tree design...remove the letter in editing software and then replace the letter with the one you need...usually in FSL, the letter would stitch last and would be fairly easy to edit and exchange with the letter you need...