Fatal disk corruption from Snow Leopard incompatibility

Question

Hello to all --
After upgrading to 10.6 from 10.5.8, I have consistently encountered a fatal error:
System extension cannot be used
The system extension "/System/Library/Extensions/IOPCIFamily.kext" was installed improperly and cannot be used. Please try reinstalling it, or contact the product's vendor for an update.
This kernel extension's vendor seems to be Apple. I can't find this kernel extension among the 10.6 packages, however, and cannot therefore reinstall it.
Worse, once this error is reported, the boot disk has been hopelessly corrupted. Disk Utility reports incorrect block counts, an incorrect number of file hard links, or overlapping extents. Neither Disk Utility, TechTool Pro, nor Drive Genius has been able to repair a disk corrupted in this manner. After being repaired, the disk simply hangs at the gray apple screen during boot.
I first suspected a hard drive problem, but the drive passed all the comprehensive tests in my arsenal. Similarly, all of my computer's systems have passed the most rigorous tests available in the above three disk utility programs. Also, I received the same error using a completely different boot disk, which makes system corruption the much more probable cause.
After the first disk failure, I clean installed 10.6, installed my main apps (the latest Final Cut Studio, Illustrator CS4, Photoshop CS4, etc...), and made a clone of the disk. It seemed to work OK until I installed the most recent Logic Studio and various plug-ins for it. The majority of the plug-in vendors' sites assert compatibility with Snow Leopard. The one or two that are silent about it have users forums filled with reports of successful use under 10.6. I can't figure why what appears to be a PCI-related kernel extension would be affected by an audio application or plug-in in the first place. The error has been manifest in both 10.6.1 and 10.6.2. I've reproduced this error three separate times, and am done with Snow Leopard until I can solve the problem.
A web-search for the failed kernel extension hasn't been very revealing, and it's not prominent among the problem reports in Apple's various user forums, either.
Anybody got any ideas what's likely to be going on here and how I might be able to work around it? All of the software in question functions OK under 10.5.8 on the same hardware.
My system is:
2007 Mac Pro 3ghz Xeon octo, 16 GB RAM, ATI 1900XT. The only significant third party hardware attached is a MOTU Traveler firewire audio interface, with a SL-compatible driver. The last time I received this kext error, however, I was running the computer without any peripherals except the keyboard and trackball.
It's a puzzler. Hope somebody can shed some light on this. Thanks.

Answer 1

We apologize for the confusion and any inconvenience that this problem may have caused and want to thank all of you for your continued patience. At this time, we have been able to reproduce an issue with the latest iZotope installers that may affect users who have recently upgraded their Mac operating system to Snow Leopard. We will be issuing an update to our existing Mac installers immediately to fix this issue.
In the meantime, if you think you are experiencing this problem, please read and follow the steps below to fix this issue. If you have any further questions or continued problems, please don’t hesitate to contact iZotope Support directly at the following e-mail address: [email protected].
Problem:
If you have received a dialogue with the text below, the next time your computer is rebooted, the operating system may not load correctly.
“/System/Library/Extensions/IOPCIFamily.kext" was installed improperly and cannot be used. Please try reinstalling it, or contact the product's vendor for an update.”
If this occurs and you encounter a Mac system “grey screen” upon restart, please follow the steps below to correct this problem.
Solution:
1.To begin, insert the 10.6 OS X installer disk and restart the computer.
2.As the computer restarts, hold down the “C” button on your keyboard to boot from your OS X installer CD.
3.Select the language, then go to the “Utilities” menu at the top of your screen and select "Terminal".
4.Copy or type the exact text below into the Terminal prompt and hit the Return key on your keyboard.
ls /Volumes
5.At this stage, a list of available hard drives should appear.
6.Next, copy or type the exact text below, including quotes, into the Terminal prompt and hit the Return key on your keyboard.
cd "/Volumes/Macintosh HD"
*Note: If you have renamed your boot drive, please replace the “Macintosh HD” in the text above with your updated drive name.
7.Next, copy or type the exact text below into the Terminal prompt and hit the Return key on your keyboard.
sudo chmod 644 System/Library/Extensions/IOPCIFamily.kext/.* && sudo touch System/Library/Extensions
8.Finally, close the Terminal window and restart the computer.
9.Once rebooted, you are free to continue as normal and this problem will not return.
Alternate Solution:
1.If you've seen the dialog box described above, and have not yet rebooted, go to your "Applications -> Utilities" folder and double click "Terminal".
2.Next, type the following command into your Terminal prompt and press the Return key on your keyboard.
sudo chmod 644 /System/Library/Extensions/IOPCIFamily.kext/.* && sudo touch /System/Library/Extensions
*Note: If prompted with the warning below, please enter your user account password and hit the Return key to continue. (Administrator account required)
"WARNING: Improper use of the sudo command could lead to data loss or the deletion of important system files. Please double-check your typing when using sudo. Type "man sudo" for more information.
To proceed, enter your password, or type Ctrl-C to abort.
Password: "
3.Once complete, you are free to close the Terminal window and continue as normal. The problem will be fixed and will not return.
Thank you again for your continued patience in this matter and please contact us directly at [email protected] if you have any questions or concerns.
-The iZotope Team