My L 4 Library suddenly shows only the first thumbnail in a catalog. All the rest of the thumbnail windows are grey. Only thr last import sghows the full catalog.
I think you are using the word "Catalog" incorrectly here. Perhaps you mean Collection? The Lightroom catalog is the database that runs the application. All of your images in Lightroom are in a catalog, there is no separation of first or last, recently or previously imported. The last import would not have it's own catalog.
I am having the same problem as Abe is. I only have one Catalog and in that catalog I have 86,000 images. For some reason, these "minimal" thumbnails or previews seem to get deleted automatically each time I reopen LR4.
Like Abe, I see the first few previews in each folder but the rest are gray boxes. To try and push Lightroom to render them again, I go into grid mode, slide the thumbnail slider all the way to the left to make them very small so that 200 images show up on my lightroom window. Then in about 5 minutes these 200 images all render a minimal preview and the gray boxes are gone.
Why doesn't Lightroom keep all these minimal previews in the preview.lrdata folder so that I don't have to redo this each time. When I was using Aperture, all the images rendered a small "minimal" thumbnail on import and they remained there forever. (That, by the way, was the only advantage of Aperture). I love LR4 otherwise.
Thanks for any insight you might have on this.
They are supposed to remain there forever. That's the point of having preview.lrdata. It sounds as though the files are not actually being saved, but are instead loaded into the temporary memory (RAM), which is lost once you close the application down. Try logging into a new user account and open your catalog there, see if the previews actually save correctly.
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