10.6.8 update caused ethernet outage
A brute force way of dealing with this is to call Apple and open a ticket.  I've done this in the past on Macs w/o Applecare.

The upside is they are best positioned to help you and it puts you in the best position to get it resolved.  

There's a fee if you don't have Applecare.  My suggestion is to agree to the fee and  after they've got you up and running, ask that they to waive the fee in light of whatever they had to do to fix the problem.