If $length in /<path_to_wiki>/inc/JpegMeta.php line 926 is evaluated to 2, then it will be reduced to zero in line 933. This causes:
"Warning: fread() [function.fread]: Length parameter must be greater than 0. in /<path_to_wiki>/inc/JpegMeta.php on line 960"
I've attached a file that causes this e.g. in the media manager.