Hi to all! It's the second time during the last year... and the first time, I had to throw away the disk and buy a new one, there was nothing to do, not even format it. Suddenly, the Time Machine disk is having a problem. Disk Utility can't repair it, it tells me to format it. I'm getting fed up with that problem... I'm using different other external disks and I never have any problem with them. It seems to be a Time Machine problem. OS 10.10.5 Thanks for your advice!