So something strange has happened to my time machine backup. The backup repeatedly was reported as having being "delayed" and would not backup even if I told it to manually do so. I then tried to "change disk" and re-select the existing drive in case that fixed it. Unfortunately my mac doesn't seem to recognise that it is a time machine drive and wants to erase everything and start again. The problem is that I have months and months of back records on the TM drive so I would rather not have to erase everything and just have the current backup. There is nothing wrong with my drive as fas as I know. I did just get the mac back from the apple store (logicboard was replaced) and had to re-authorize iTunes. It is my first attempted backup since then. I don't know if that is related. Has anyone else had similar problems or is aware of a fix? I am not sure what to do. Any advice would be most gratefully received.