Cannot Upload Image Into Post

Have looked through other posts and there have been plenty of problems with uploads, but mine is a little different. When I click on the Upload/Insert button to load an image direct into a post, I get what looks like a popover screen with the message “Are you sure you want to do this?” and below in highlighted text “Please try again.” Click that and it opens another window like the original. Click the Upload button in that window and I get the same popover screen, like a set of Russian dolls.

I can load images into the library, but cannot get them into a post.

Any thoughts?