I was working on someone's 2.33 Ghz MBP today. Their problem arose when they tried to install 10.5.6 through Software Update, though it may have been coincidence. On the reboot after installing, it got a kernel panic by the time it got to the grey Apple logo. After holding down the power button and turning it on again, same thing. When I got the computer I tried booting into safe mode. I held shift until I got the spinning wheel below the Apple logo, and then it gave me an error symbol. Circle with a line through it, to be specific. After booting using the Leopard disc, I found that I could not erase or partition the internal drive. I tried many things until I found that the Gparted live CD could reformat it. After I reformatted the drive (160 GB) using Gparted, I zeroed out all data before I reinstalled Leopard. After it was finished installing, I clicked restart. Now normally the computer would restart seconds after clicking, but instead I got stuck on a grey screen with only the cursor visible. I left it for a long while before finally holding down the power button to force a shutdown. When I turned it on it got stuck at the spinning pinwheel and Apple logo. I left it for another great while before finally using the power button again. The next time I booted using verbose mode and got an error loading the driver appleyukon2.kext, which is located inside IONetworkingfamily.kext. It would just sit there until I shut it down. So now I arrive at my conclusion and question. I am at a loss as to what is wrong with this computer. I found that appleyukon2.kext has something to do with the wired ethernet port. Could it be the ethernet hardware is at fault? My other thought is that it could be the hard drive. S.M.A.R.T. status is fine and the install went flawlessly until the grey screen, so I don't think it could be that. If anyone could shed some light on the subject it would be greatly appreciated.