graphics no longer uploading in WP

Am I ever going to get a response to my question of a couple days ago? I checked the files back two days and didn’t find it, so perhaps that’s the reason.
Suddenly when I go to Set Featured Image in WP’s Add New Post page, and select a .jpg graphic off my desktop, absolutely nothing appears. First this was happening when somehow the .jpg suffix got dropped from the graphic file in Elements, but now it happens all the time. (Perhaps WP was deleting the suffix; not Elements.) It prevented me from uploading daily articles to my web magazine (closing down operations completely), until I discovered that by quitting Safari and then restarting it, the graphics uploading worked again. But this is not normal. I can’t do that for every article I upload. What could be causing it?