[Mediawiki-l] Warning: imagejpeg()...: Unable to open thumb

[Markus Klaus Schäffauer]

Hi,

we get the following error message on 
http://www.vdr-wiki.de/wiki/index.php/Sysinfo-plugin :

    Warning: imagejpeg() [function.imagejpeg
    <http://www.php.net/function.imagejpeg>]: Unable to open
    '/www/htdocs/v101777/wiki/images/thumb/8/89/180px-Sysinfo-plugin.jpg'
    for writing in /www/htdocs/v101777/wiki/includes/Image.php on line 232

How can we avoid that error?

Thank you,
Markus