I have had lots of troubles with Time Machine since the "upgrades" to Lion and Mountain Lion. I have several Macs and only one has not had this problem with Time Machine that requires a reinitialization of the hard drive. The message is: I have repaired the disks with Disk Utility, restarted the computers, reinitialized the Time Machine hard drives, turned them off and back on, but nothing seems to fix this problem. Are there alternatives to Time Machine that are more reliable? I have to have a backup system in place and Time Machine simply is not the solution because it cannot be trusted to work.