2.7/sparc networking problems

[Jeff Wyman <wysoft_(_at_)_wysoft_(_dot_)_tzo_(_dot_)_com>]

I have a really confusing problem here with my previously happy
SPARCstation 2 running 2.7.

Story: I moved the workstation from my home into my office at work. I set
it up, and knew that I'd have to modify the network configuration, so went
to the wiring closet and grabbed both the DNS and wiring diagrams to see
which jacks and IP addresses were available. However, when I booted the
machine I found that the fb was somewhat broken because of a ROM caching
nvramrc that I snatched from the NetBSD/sparc FAQ. After restoring the
NVRAM to it's previous condition, I was able to get into the machine and
configure it for the network.

Problem: I couldn't get any network access. Even after confirming that the
IP address was unused and using the machine on a working jack, I couldn't
get to the network. I could receive a DHCP lease from the LAN's DSL
gateway, but after that I couldn't do anything at all on the network -
despite the fact that my AUI adapter clearly showed a link and receive
activity, along with send activity when trying to ping. I ran to the hub
in the wiring closet, and saw little activity coming from my link.

So basically, wether I obtain a DHCP lease or menually plug in addresses,
I get nothing.

What I tried: Well, I tried booting the GENERIC kernel. Nothing. I
repeatedly tried new addresses, checked cabling drops, fiddled with my AUI
adapter. Strangely enough, I found that when I run tcpdump, I received
data. I launched X and just by coincidence I ran a ping while running
tcpdump. It worked! It appears that I can access the network and get out
to the internet when the interface is in promiscuous mode.

Weird evidence: stations and servers on the network that I pinged seemed
to know my MAC address when I ran "arp -an". I couldn't find theirs. It's
almost like my interface isn't accepting data when in non-promiscuous
mode, but there is a catch: even in promiscuous mode, no other stations on
the LAN can ping me or telnet in, but I can ping them and telnet in to
them!! I'm just stumped.

Now, does anybody have a single clue as to what's going on here? I'm just
about to install Solaris on a separate drive and see what I get, but I
don't want to ditch OpenBSD in this environment, and I simply don't have
the time to do so for "experimental" purposes while I should be 
administering servers from this machine, which I can't do atm :( 

Solaris is just too bulky and slow for my tastes.

THANK YOU for any info,
Jeff