This weekend, I learned the hard way that trying to jailbreak an iPhone 3G using a MacBook running 10.5.6 can totally freeze up the machine later on. Here are the specifics: UPDATED
Short version: Be careful with that latest QuickTime update if you have run any "DFU fix" Automator scripts on your unibody (Late 2008) MacBook or MacBook Pro. Do not upgrade to QuickTime 7.6 until you've repaired the alterations that the script made to your system. UPDATE: I am learning from commenters that this is not just limited to unibody Late '08 MacBooks, but it applies to ALL MacBooks running 10.5.6.
In this post, we outlined how to re-enable unlocking and jailbreaking functionality if you've upgraded to Mac OS X 10.5.6. To do it, you have to run an Automator script that "fixes" the system so that you can enter something called DFU mode. It's some hardcore juju, but the script seemed easy enough to run and reboot.
The now-mysteriously-missing original Hackintosh article mentioned that there were some issues with the unibody MacBook and MacBook Pros, but it never said that you should undo it after you finish jailbreaking.
I didn't even get the jailbreak itself to work on that machine in the end, even though Jason did on his unibody MacBook Pro, but the Automator DFU fix didn't cause any perceptible changes to my system's behavior, so I promptly forgot about it.
Fast forward two weeks. I get a notice of the latest QuickTime upgrade, so I OK it. When my system restarts, I have no access to keyboard or trackpad. Not only do I not have access, I can't even plug in a mouse or keyboard. I could use those controls when booting off of a system install disc, but I couldn't get the installer to repair my OS, since it was "newer." The computer was borked.
My solution was easy but nuclear: I turned an external 320GB drive into a boot disk, ran the migration tool to move every bit of data from my unibody MBP, then simply swapped drives. (Gotta hand it to Apple for that new swappable-drive design.) My machine is as good as new, and now totally up to date.
What you should do, if you already ran the DFU script and haven't installed that QuickTime update yet, is try the method I have since discovered outlined in this Apple Support thread. Apparently, I'm not the only one with this problem.
Here are a few solutions besides the one in the support thread:
• If you still have access to your keyboard and mouse, you can copy the backup files (it should be under Backup_IOUSBFamily_kext_10_5_6 on your desktop) to where the Automator script was, Install_IOUSBFamily_kext_10_5_5 on your desktop. Then, just run the Automator script again, and it will copy those "original" files to the right location, then change the permissions correctly and reboot your machine.
• If you already ran the QuickTime update and you're unable to access any input (USB or otherwise), you can SSH into your machine and run these commands one by one. If you had trouble with the Automator script, you can open up the terminal and do this too, manually. Note, some of these lines are too long, so they wrap to 2 lines. Make sure you copy it in its entirety. Commands are separated by empty lines in between.
sudo rm -R /System/Library/Extensions/IOUSBFamily.kext/Contents/PlugIns/AppleUSBHub.kext
You'll have to enter your administrator password here
sudo rm -R /System/Library/Extensions/IOUSBFamily.kext/Contents/PlugIns/IOUSBCompositeDriver.kext
sudo cp -R $HOME/Desktop/Backup_IOUSBFamily_kext_10_5_6/AppleUSBHub.kext /System/Library/Extensions/IOUSBFamily.kext/Contents/PlugIns/
sudo cp -R $HOME/Desktop/Backup_IOUSBFamily_kext_10_5_6/IOUSBCompositeDriver.kext /System/Library/Extensions/IOUSBFamily.kext/Contents/PlugIns/
sudo chown -R root:wheel /System/Library/Extensions/IOUSBFamily.kext/Contents/PlugIns/AppleUSBHub.kext
sudo chmod -R 755 /System/Library/Extensions/IOUSBFamily.kext/Contents/PlugIns/AppleUSBHub.kext
sudo chown -R root:wheel /System/Library/Extensions/IOUSBFamily.kext/Contents/PlugIns/IOUSBCompositeDriver.kext
sudo chmod -R 755 /System/Library/Extensions/IOUSBFamily.kext/Contents/PlugIns/IOUSBCompositeDriver.kext
sudo rm -r /System/Library/Extensions.mkext
sudo touch /System/Library/Extensions
sudo reboot
Your machine will reboot after prompting to update boot caches, and the files should be back to the standard 10.5.6 ones. Good luck!