I am using Linux Mint and am having the following issue. Firestarter tells my that my firewall is active and it does indeed seem to be active. However when I type "sudo ufw status" into the terminal, I get the response "Status: inactive". It is my understanding that Firestarter is merely a way of controlling ufw. So, why the discrepancy?
Both Firestarter and ufw are front-ends for iptables. My understanding is that Firestarter hasn't been developed in some time and is quite buggy (last stable release in January 2005). If you are running both, one is likely conflicting with the other. I would uninstall Firestarter and use ufw. It is more reliable and under active development.