I guess that means the DPI is too low? I don't have a scanner at my current location, so I used a camera to take a (good) picture of my DL. I'll have to go to a public library to scan it tomorrow, unless there's some simple way to change the DPI on my pictures.
I would be very surprised if your guess is true. Doing so would require the upload to be successful and some automate process to analyze the image. My guess is that whatever server Gox is running to accept uploads has a full disk or something equally stupid.
I've tried several times now, and it still doesn't work. So I guess it really is the 300 DPI thing after all.