Existing users, 
I, too lost my ethernet there are several reports of success by reverting to the old AppleGMACEthernet.kext. The old one 1.2.4 seems to work fine, the 1.3.0 doesn't connect for Gigabit Ethernet machines.
Apple Mac OS X
operating system (PPC)
Version: 10.4.11
Gigabit Ethernet machines: revert to old KEXT...
Feedback Type: Troubleshooting Report
Contributed by: White Rose Monday, September 22 2003 @ 08:32 PM PDT
Product Platform: MacOSX
Used Product For: Have Not Tried
System Info:
Comments
Gigabit Ethernet machines: revert to old KEXT... - White Rose
These instructions were posted to the Apple Discussion Board. YMMV, IANAL, Objects in Mirror Are Closer Than They Appear. But it worked for me. I grabbed it on my wife's Powerbook, put it on her iPod, mounted the disk on my desktop, and then followed Andrews' instructions, including backing up the .kext file. I've been back in business for a few hours now.Monday, September 22 2003 @ 09:53 PM PDT
Gigabit Ethernet machines: revert to old KEXT... - MARVINBASS
Yes reverting back to the older extension brought back my connection. I assume Apple has beta testers, how could this get passed them??Monday, September 22 2003 @ 09:17 PM PDT
Gigabit Ethernet machines: revert to old KEXT... - churchoflambda
Where can I get a description of how to "revert" these files?Reply to This
Monday, September 22 2003 @ 08:43 PM PDT