I'm looking at my parents iMac via Apple Remote Desktop and noticing that their Time Machine backups are not working. It seems the last successful backup was about a month ago when I was there, I plugged it in before I made some changes to their setup and added another mac to their house. During the tweaks I was making, since i added another mac (a MacBook), I changed the iMac's computer name to simply "iMac" from "C*** R*****'s iMac". It seems the iMac has not had a successful Time Machine Backup since that day. The 500gig external drive is intact, I've run diagnostics on it and it all checks out fine. Any suggestions?