Another problem with images

I think others have had the problem, but I have not been able to locate a thread indicating how to fix it.

When I drag album cover images to the space indicated for the album, they initially appear with no problem. However, when I close the program and reopen it, most of the images are gone. Only a very few remain.

I have moved the images to a fixed directory, but this does not fix the problem. I have tried resaving the images from an image processing program to no avail. And, I have no idea why some images stay, but most disappear.