Dude you're doing it all wrong, this exact same thing happened to me a few days ago coz of what I've read in the monowall documentation regarding 1:1 NAT, it's not complete. Although you can mix port forwarding rules with 1:1 NAT, it is not necessary as long as you have that many public ip's available.
This is the procedure you should follow:
1. Create the Virtual Ip's.
2. Mapped the public ip's to the virtual ip's you've created in step 1.
3. Finally create firewall rules allowing a particular service that your server will be providing, (let's say that is a web server) create a firewall rule in your WAN interface allowing tcp port 80 from anywhere to the private ip address of the web server.
e.g.
TCP * * 192.168.1.2 80(HTTP) *
You also ought to read this thread about 1:1 NAT -> http://forum.pfsense.org/index.php/topic,6965.0.html
HTH