I have been trying to do a backup with Time machine onto my external hard drive. It starts backing up (it has managed 1GB out of 31GB) and then the message appears "Time Machine Error" - "Unable to complete backup. The backup volume may have been ejected or disconnected from your computer" My hard drive icon then disappears from desktop, finder, and disc utility. On the time machine window it says "Next backup - when disk is connected". This has happened on several attempts and I have to shut everything down to enable me to try again. Oh and sometimes I get another message flashing up telling me that the volume wasn't ejected correctly or something like that. I have erased the external drive and have 149.0 GB available. I have tried using different USB ports. Can anyone tell me what I am doing wrong. Forgot to mention I am using a MacBook Pro (10.5.8) Many thanks in anticipation.