Once you import files, the software creates thumbnails for the given files. From my understanding, it seems that the application reports errors to the images because they have been deleted/moved from their original location when you imported them. To solve the problem, you either move the photos back or simply import them from their new location if it’s the case. Also, an inappropriate reset of the computer while everything was working properly or a power down failure might have been caused this to some of the files which in this case there is nothing to do than to copy the original files back to your hard drive if you have a backup copy.
