I have been using Time Machine on my mac ever since I got it in June, and yesterday while it was automatically backing up and it pops up and says Backup failed something something. Well no big deal that has happened a couple of times before, so I just click back up now.....and it doesn't work. Then I unplug the HD and plug it back it, same thing. Now the HD will not even show up in finder. My computer does not even know it is there. It lights up and everything when I plug it in, but nothing happens. I have a ton of files on there too, not only Time Machine..... what do I do?