The title says it all really.
Attempting to upload image(s) via the "Files" tab results in an internal server error. The images appear in the "Edit & organise" section with 0% complete, and an error appears for each file. It doesn't matter if I use the "choose files" button or the Drop Area.
I suspected that it was a permissions issue (which I used to get on older versions of SS), but changing folder permissions doesn't help.
Screenshot attached for further clarification. All advice gratefully received :)