It runs the image through a converter to create the thumbnail. That is the thing that seems to crap out. It gives a message that it can not determine the image size. What software are you using to create the jpg? I could be related to that...
Originally Posted by tilt
Gimp, always. And if i just save another jpg it almost invariably doesn't work. For some reason fiddling with the quality percentage makes a difference. maybe it's a bug or slight difference in the way gimp compresses the jpg?