Hi,
Please check the xml/_mydebug.out file.
It seems the gd library cannot process your images properly.
he debug file should tell you if there is a problem.
Maybe memory, maybe the image compression!
Sometimes resizing with a external tool to he same size but slighly differeny compresssion works fine.
I always use cam2pc
http://www.nabocorp.com/cam2pc/freeware.php
for this because it keeop the exif data Smile.
And you shouldn't access TWG while uploading images!
If you delete the black images they are regenerated - if they are still black then the debug file gives you more details!
/Michael