Did you check if it's in the finder? Or if you know how, you can use the terminal. By the way what do you mean by If it's not there, then that's probably the reason why it won't show. I've had this problem a few weeks ago, and it took me a long time to figure out what was happening.

It's not in the finder even after I use "import from file." I mean that I create the image in Photoshop and save it to the folder labeled "images" that is automatically created inside the scenario folder when you create a new scenario. After that I go into Greenfoot and select it using "import from file" and it gives me the error. When I return to the folder, the image is gone even though it was there before I told Greenfoot to use it. I just tried saving it to my desktop and opening it from there and it works, but of course it isn't in the Scenario Images finder because it's not in the folder. (And I want it to be, but the aforementioned error occurs when it's in that folder) Edit: It just added the image to the finder area after I redid everything and uploaded it from my desktop. I still can't upload an image from the image folder without getting the error etc. Edit 2: But it's there before I try to upload it. It's as if Greenfoot deletes the image when it gives me the error.

Does it happen with every image or just with this one? Try to set the image manually instead of right-clicking the class.