It look's like the reason for the error was the url. With a direct link to a file from my appache server I have no problems.
&action=upload
&filename=T2.png
&url=http%3A//localhost/t2.png
&ignorewarnings=1
&token=%2B%5C
&format=xml
Thanks for helping me!
Stephan
Von: "stephanheyne-wg@yahoo.de" <stephanheyne-wg@yahoo.de> An: MediaWiki API announcements & discussion <mediawiki-api@lists.wikimedia.org> Gesendet: Dienstag, den 11. August 2009, 13:02:41 Uhr Betreff: [Mediawiki-api] WG: Image upload fails even with example Request
Now I have set the user rights of group all: now its allowed to every user to upload files and upload from url.