No, you don't need to reinstall. Go to the folder where your catalog is located and delete the folder that has the .lrdata extension. This is your previews folder. Now, start Lightroom and it will start to build a new previews cache.
I will give it a try.
My "Lightroom 5 Catalog Previews.lrdata" folder is 12.3 GB in size, so the rebuild will take lots of time...right?
I'll let you know how it goes.