I have same problem since last week, reported it through "contact" but no answer yet.
Since the new website started I was uploading photos singly with my browser (Google Chrome, using the "open" button for the file) without problems, but the first time I tried to bring up two photos at once, I got a warning that "parameters are missing" and there were no thumbnails in the "drop up" box It's now the same whether I try one photos or multiple
HOWEVER, seeing Foggy's comment of yesterday I just tried the "click & drag" method and it worked OK
Jackosan