note 24130 rejected from function.imagecreatefromjpeg by jmcastagnetto

I wrote an upload script to put jpeg images on my server. I limited the maximum filesize to upload to 2Mo. This thing works, for some files, and doesn't for others. All the files I tried to upload are jpeg, from 20Ko to 1.5Mo. I use ImageCreateFromJpeg in this script, and I get this error (when it's not working) : 'fileName is not a valid JPEG file', which, I know, is not true... Is there any limitation using this function (image resolution, image size ...) Thanks, Jaad