Ask in the LR forum and provide proper technical info like system specs and where your cache is stored. You are expecting people to operate on generic assumptions and vague descriptions and have not provided proper tech details.
"Ask in the LR forum and provide proper technical info like system specs and where your cache is stored." Is that a question or a statement? There is no subject in this sentence. A sentence is composed of a subject and a predicate. But I think I know what you are asking, although you are somewhat lacking on social acumen.
My PC is running Windows 7, with the latest update on a Dell with 8 GB DRAM, 1TB HD with 400 GB of free space. I am running LR v 5.5 64-bit. The problem started after I updated Adobe CC. So, throw me a bone so I can figure this out.
Try renaming your Preview Cache Folder with a .OLD extension:
Lightroom 5 Catalog Previews.lrdata.OLD
The folder location be found here under 'Preview cache' Preference and other file locations in Lightroom 5
This will cause LR to build a new Preview Cache. If it resolves the issue you can delete the renamed OLD folder: Lightroom 5 Catalog Previews.lrdata.OLD.
If the problem is not resolved do NOT delete the renamed OLD folder. Let us know and will try to help further.