For the Upload Problem with jpg Files,
you should edit your upload_definitions.php in includes folder:
Replace this:
$mime_type_match['jpg'] = array("image/jpeg", "image/pjpeg");
$mime_type_match['jpeg'] = array("image/jpeg", "image/pjpeg");
with this:
$mime_type_match['jpg'] = array("image/jpg", "image/jpeg", "image/pjpeg");
$mime_type_match['jpeg'] = array("image/jpg", "image/jpeg", "image/pjpeg");
P.S.:@admin, is there any reason why this were changed?