Fixed it by adding an .htcaccess-file.
My own php.ini, made for PHP 5.2 overruled the central php.ini made for PHP5.3. The MySQL-functionality was included in the server configuration, but my own php.ini turned it of. The solution was to remove the php.ini from wp-admin.
My host is not able to increase the memory size in php.ini (it’s currently at 48M), and they claim that there is nothing they could do.
“It got nothing to do with the used space on the webhotel. It’s the process of uploading the file and the file itself that takes PHP memory.” they say.
But why does this upload suddenly takes so lot of memory? Do I have to return to Drupal to get a proper working blog?
If i remove the line 258 in media.php the error disappeares, but the images are then not crunched, and is uploaded in full size.