> I have not experienced this with m0n0wall specifically, but it has
> happened numerous times with other routers doing nat with port
> forwarding. I had a similar setup to yours and for some reason port
> 8080 would not forward. It turned out the web interface for the
> router itself was on 8080. Upon changing it, everything worked
That was exactly the problem: I have changed the port of the WebGUI.
Now NAT works fine for port 80 and 443.
Thanks for the numerous hints!