Moving this discussion to the Photoshop Lightroom forum.
Did the error message refer to the "previews cache" this is different to clearing the cache i.e "the Camera Raw Cache"
See the attached screen capture which will show the location of the "previews folder".
If you delete the file highlighted and ending with xxPreviews.lrdata, Lightroom will build new previews to replace the corrupted ones.
Thank you so so so much! I was having the same issue and now after deleting that file it runs great!
Hear, hear! I got my LR working imediately after fixing this.
Best wishes and thank you!!!