I've inherited a site built with Drupal, moved it to a different server (from Ubuntu Server 9.10 to Ubuntu Server 10.04) and now I'm geting the following error when I trying to upload an image via an ImageField.
„160284.jpg” nem tölthető fel. The file is not a known image format.
The first (localized) part of the error is „160284.jpg” cannot be uploaded."
I've noticed that the second part of the error is not true. It is generated in filefield_validate_is_image() and is caused by the file referenced in $file->filepath missing.
File permissions shouldn't be a problem because right now everything is just 777. The temp directory is writable too.
What is causing the error?