http://upload.wikimedia.org/wikipedia/commons/thumb/c/c8/Kodak-Vollenda620-d...
gives
Error generating thumbnail
Error creating thumbnail: /usr/local/apache/common/php-1.5/bin/ulimit4.sh: line 4: /usr/bin/convert: No such file or directory
On the next try: Error generating thumbnail
Error creating thumbnail: convert: Insufficient memory (case 4) `/mnt/upload3/wikipedia/commons/c/c8/Kodak-Vollenda620-detail.jpg'. convert: missing an image filename `/mnt/upload3/wikipedia/commons/thumb/c/c8/Kodak-Vollenda620-detail.jpg/166px-Kodak-Vollenda620-detail.jpg'.
Note that this is the Commons picture of the day, so a failure to generate a decent-sized thumbnail from it is rather serious from a user perspective, IMHO.
Magnus