Before:

ex0 at cardbus0 dev 0 function 0: 3Com 3c575B-TX Ethernet
ex0: interrupting at 11
ex0: MAC address 00:00:86:34:11:6f
tqphy0 at ex0 phy 0: 78Q2120 10/100 media interface, rev. 3
tqphy0: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto

After:

ex0 at cardbus0 dev 0 function 0: 3Com 3c575B-TX Ethernet
ex0: interrupting at 11
ex0: MAC address ff:ff:ff:ff:ff:ff
tqphy0 at ex0 phy 0: 78Q2120 10/100 media interface, rev. 3
tqphy0: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto

An all 1's mac address does not make a happy network ;-)

It was working with source from the 15th of March and broke after an update
on the 2nd of april - I guess this happened when support was added for the
3c555, 3c556 and 3c556B MiniPCI Ethernet cards, but i can't see anything
obvious from a diff.

pr: kern/12557

-- 
     "The aurochs was the great, black bull that was painted on cave
walls  alongside bison and mammoths  by tacky prehistoric minimalist
artists  who  had no  sense whatsoever of  modeling or perspective."
[see: http://www.aristotle.net/~swarmack/aurochs.html]  [0x2ECA0975]