[Mediawiki-l] upload directory changed

[WikiPlant]

I have a problem: i changed in LocalSettings.php the upload 
directories... and now there are coming warnings, e.g.:
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Warning: 
imagecreatefromjpeg(http://upload.wikiplant.org/de/b/b2/Helianthus_annuus_(1).jpg): 
failed to open stream: HTTP request failed! HTTP/1.1 404 Not Found in 
/www/htdocs/w005dd98/wiki/includes/Image.php on line 1071

Warning: imagecopyresampled(): supplied argument is not a valid Image 
resource in /www/htdocs/w005dd98/wiki/includes/Image.php on line 1079

Warning: imagejpeg(): Unable to open 
'http://upload.wikiplant.org/de/thumb/b/b2/Helianthus_annuus_(1).jpg/450px-Helianthus_annuus_(1).jpg' 
for writing in /www/htdocs/w005dd98/wiki/includes/Image.php on line 1099

Warning: imagedestroy(): supplied argument is not a valid Image resource 
in /www/htdocs/w005dd98/wiki/includes/Image.php on line 1082
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please help me :(

second question: what have I exactly to change for making shared uploads 
from several wikis possible? (i know, something with the 
deafultsettings, but what?!)

thanks for your help and greez from germany - florian*
*