Where are the images located? Are they on a local drive or external?
Also which version of Lightroom are you using? If you are using Lightroom CC can you try the same in Lightroom 5
Please share the results for the above asked queries so i can further help you out.
Thank you for posting on Adobe Forums.
I’d suggest deleting your entire previews cache outside of LR. To do this:
1) Find the LR catalog folder. If you don’t know where it is, the path is listed in LR / Preferences / Catalog Settings.
2) Exit LR, and make a backup on the way out of LR.
3) Find the catalogname Previews.lrdata folder and delete it using an OS function.
4) Restart LR.
Make sure you DO NOT DELETE THE LRCAT FILE. This is your LR catalog.
The images are on a local drive. I'm using Lightroom CC currently, but the same problem occurred in Lightroom 5, which I was using up until 2 weeks ago.
I deleted (renamed) the Previews.lrdata and so far it seems to have helped... I won't know for sure until a few days of using it and making sure I don't come across the problem again.