LAN unreachable after 5.3 install

[Wes Santee]

Greetings all,

I've just completed update from 4.9 to 5.3 and so far not much is
working.  I went the "format and install" route to minimize
incompatibilities.  After the install, the first thing I wanted to do
was get my network up and running.

I've got a pretty standard setup: LAN on one NIC, PPPoE Internet on
the other NIC with NAT addressing.  Ignore the PPPoE and gateway side
of things for a bit, my problem is that after install, I can't see my
LAN.  From the FreeBSD box I try this:

ping -S 10.0.0.1 10.0.0.254

but none of the pings are responded to.  From 10.0.0.254, I try
pinging 10.0.0.1, but the result is the same.

Okay, here is the WEIRD part:  When I run tcpdump to see what's going
on, all of a sudden everything starts working!  It's as if going into
promiscuous mode shuts off some kind of block that I can't figure out.
 When I kill tcpdump, it goes back to not working again.

Any ideas what is causing this or how to fix it?  I strolled through
the install notes, but I don't even know what I'm looking for.  That
makes searching the mailing list archives difficult also.

Cheers,
-Wes