I'd be surprised if it's the zone alarm firewall -- easy way to check, try disabling the firewall and running a bittorrent. Further, should be easy to adopt the zonealarm pro instructions to the non-pro version.
Question -- what make/model dsl modem do you have? Many of the dsl modems being shipped these days have an internal firewall (aerscom, etc.) and its settings need to be modified to allow port forwarding.
Also re connection rate -- sometimes that's just how things work (i.e. a slow torrent) -- firewall issues generally result in a VERY slow upload speed -- were you seeing any real upload activity on your torrent?