Large image size bug?

[shopgirl]

If I go to Preferences > Images and make the max size 1024 width, 1024 height then it works, and I get images that are 1024x1024.

However, I am interested in having images that are 1280x1280 or higher. When I put in 1280 width and 1280 height, then my uploads fail. It doesn't show me "Upload Successful" and the thumbnail will be present but the image will be a question mark (404). I tried it like 20 different times with different size settings, different source photos, etc before I reached this conclusion that this is what's happening.

I even tried making a type named supersize instead of using the one labelled thickbox. Same problem. Works great if my max values are 1024, doesn't work if my max values are 1280.

Maybe it's something to do with my server? But in searching, I found others who were having this kind of issue with prestashop. When trying to upload pics over 1024.

I'm using the latest 1.3.1.1.