I would look at the vlan and mcast forwarding code, and make sure that
the multicast packets end up with the mbuf rcvif pointer pointing to
the vlan struct ifnet, rather than ex0's, at least by the time the
packet is sent to ip_input.  Also, the way vifs are mapped to struct
ifnet feels a bit unusual to me, but that part looks ok.

I wonder if vlan1 and vlan3 should have ALLMULTI set.

PIM should not be necessary for mrouted.

Your status output looks quite different from my 2.99.15 system.

Make sure the TTL of the data packets is >1; often multicast programs
don't set it higher by default.

-- 
        Greg Troxel <gdt@ir.bbn.com>