I had to take my computer to the apple store because the hard drive was completely full! They sold me an external hard drive and told me to transfer all my pictures. So I did but now my lightroom 4 pictures don't come up on the external hard drive and when I access it through my hard drive it says offline?? I have tried to locate pictures but it doesn't seem to work???
Any chance that the external drive is configured to "sleep" when not in use?