I have Time Machine backing up to an external drive, connected by USB. Today I noticed that my iMac doesn’t make time machine backups anymore. The backup starts but hangs after a while. It has to backup 2GB and stalls at a few hundred MB every time. I find it very strange, this happens out of the blue. I never had problems with time machine before, is has been working reliable for years. I tried several things to solve the problem: PRAM reset, didn't help NVRAM reset, didn't help unmounting my external HD, remove the time machine plist file, reboot iMac and mount the external HD again, didn't help Check my external drive with disk utility, drive is OK Check my internal drive with disk utility, drive is OK I also tried time machine backup to another external drive, but this stalled also Anyone a suggestion how I can solve this? Thanks in advance.