After an update to 10.6.8 my ethernet stopped working. I understand this affected millions of mac users. Is there a way to revert in OSX? This is the newest MBP 13" 2.7 GHz i7.
I would go here 10.6.8 Combo updater from Apple and download it via wi-fi and then re-run it. This often will fix whatever issues occurred with a Software Update via the built-in app.
A word of caution is to have a backup before doing this.
If you have a Time Machine backup that would be the easiest way to revert.
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.