Today it made clear to me why Garvin Hicking is called "SuperGarv". I've had a little problem with my s9y installation and asked Garvin by mail, because I know him since good old Grafik.Ger times in FidoNet.
The problem has been described in #502954 as well: you can create directories in the Media Manager, but you can't see or use them afterwards, although they are there in the filesystem.
Usually, one could have solved this by yourself, but it seemed more apparent that the application is buggy. Garvin, instead, got the idea pretty soon:
Hast du vielleicht nur Schreib- aber keine Leserechte für die Verzeichnisse?
Translation: "Do you have just write but no read permissions for those directories?
It's in fact somewhat unusual that you can create directories, but cannot use them afterwards. Especially when you see them on disk, you are likely to suspect a problem in the application itself, not on the disk.
But Garvin was right:
#ls -l /usr/share/serendipity/www/
lrwxrwxrwx 1 root root 28 2008-12-02 09:18 uploads -> /var/lib/serendipity/uploads
# ls -l /var/lib/serendipity/
drwx-wxr-x 2 root www-data 6 2006-10-18 16:10 archives
-rw-rw---- 1 root www-data 0 2008-12-02 09:19 htaccess
drwx-wxr-x 13 root www-data 4096 2008-12-02 07:48 uploads
root@vserv1:/usr/local/drupal6/modules# chmod g+r /var/lib/serendipity/uploads/
I've checked with Adrian von Bidder (#502954 submitter) on IRC and this seems to be a bug in the Debian package indeed.
So, thanks to Garvin for the hinting and Adrian for the bugreport and checking on IRC! :-)