Thank you - that was exactly it.
So I guess you did pretty well to figure it out without any clues. :p
"Please select a valid image file type. The library supports .jpg, .gif, and .png files."
was the error message, the symptom was that it wasn't working specifically on Macs, and we found this out when someone tried to upload an image on their mac.
Anyway - much appreciated - not all of us come from a coding background, but more a design background, and so sometimes stuff that's second nature to you guys isn't always to us.
🙂