@Zing Thanks for your answer. I made a check, it found an error, but it didn't change anything. So I reinstalled from scratch, it rebooted, but after I said the storage is ANYEXTERNAL, same pb.
Then I said to myself maybe it's the USB key which had a pb.
Then I scanned it and it found some corrupted sectors and repaired it, now it works again.
Thanks for your help, have a nice day!