I've been struggling with Jaguar and the new sharing setups every since I installed it. At first nothing worked. Here is a list a things to check that eventually made it work as expected on my machine:
- Remove previous firewall freeware; Jaguar needs a "clean" firewall setup if you intend to use its auto-config module.
- Remove NAT that you might have installed manually.
- You'll need to "start" internet sharing manually after each reboot (I haven't found how to automate this yet - has anyone?)
- Remove rule 2010 from ipfw manually, this actually prevented other computers on my network from accessing the outside world:
02010 2 745 deny ip from 127.0.0.0/8 to any in
Just do (as root or with sudo) ipfw delete 2010.
And now, everything is "almost" back to normal. All we'd need would be a nicer way to advance-tweak Jaguar's firewall. Hope this'll help some people out there.