Microsoft just wiped and and reinstalled win 8.1. I loaded up Lightroom 5 and see only blank thumbnails. If I click on a photo I can see what's under the gray but when I click on another thumb the previous photo turns grey and I can see the current image. Of course I'm in the middle of a huge deadline. I did delete LR and reinstall a second time but no improvement. Any ideas about how to correct this?
Two possibilities: Corrupt Preview Cache or a bad Monitor Profile
1. Preview Cache is located in the same directory as your Lightroom catalog and has the name "yourcatalogname Previews.lrdata" close Lightroom. Rename this and restart Lightroom. Do the thumbnails start appearing?
If that doesn't work, reverse the name change you did in step one and then try this:
2. Set your Display profile in the Control Panel to sRGB. Do the thumbnails come back?