The application is extremely unstable for me. Even on different distributions, it tends to segfault all the time which makes it utterly unusable. I talked to two people who share these experiences so I think it is safe to assume that Firestarter simply is too old to be used in conjunction with any modern distro. I can only guess that it would still work on Ubuntu 6.06 but for Arch Linux, I think there is hardly any chance. As was already pointed out by Grigorios, the project seems dead beyond hope for maintenance patches that address these issues and since it is still sometimes suggested as a firewall application, I think it should be removed and remain removed from the repositories to avoid confusion and frustration and maybe even possible security issues.
That is entirely my fault. The devs already voted firestarter out after I brought the issue up. This package will be gone very soon as I think it just constitutes a giant hazard by disguising itself as a security application. -T