I was in the middle of 1:1 rendering when I lost power. Lightroom 5.7 would not restart because it "encountered a problem with the preview data". I renamed the existing LRDATA directory and then Lightroom started fine and created a new LRDATA file, but I had lost all my previews (of course). My question is - can I recover the previews from the original corrupted LRDATA folder?
No. You just have to let Lightroom generate new previews as you work.