Hi. I have been using Lightroom for some time. Everything has been working perfectly. I have upgraded to Lightroom 2015. Last night I imported around 72 pictures from my Nikon and they showed up as the latest import. This morning I started it edit them and as I did so, the previews all greyed out. After I had finished editing - around 3 hours work, the programme quit and so I re-opened it. All the images are gone and only the previous import of 1 image from a couple of days ago is showing. I have also noticed that the remaining previews from work last week also seem to be greying out. Can you assist me as I need to use the programme urgently and I am afraid that if I carry on I might lose any further work carried out on the programme?