I have been receiving this same message when trying to export my finished images. I tried many of the fixes listed in these threads. However, in my case, it turned out to be the catalog that had a problem. I was able to export the images by creating a NEW CATALOG, then importing the images from the original catalog into it, to then export it. Hopefully my sharing this will help someone else. Here are the steps.
File > New Catalog > (name it) Create > the new catalog will then open...
File > Import From Another Catalog > (find original catalog) Double Click to open or click Choose > (check box) Import.
Once the images have completed the import, you may export as you normally would.