Snow Leopard killed my Mac!

Pull your hard drive(s).

A, you really want/should have backups, bootable, and others.
B, I would never install an update without preventative maintenance.

At minimum boot from SL DVD and use it to REPAIR your destination hard drive first. Run the SL version of Disk Warrior or others.

Zap the PRAM/NVRAM from cold boot.

Disconnect any and all external devices and look at a list of 3rd party hardware to see if you have any that isn't compatible. Pretty normal pre-OS checklist. Internal controllers? pull those, too.

There are lists and FAQs on MacFixit, MacIntouch, XLR8YOURMAC, and others.

http://www.xlr8yourmac.com/
http://www.macintouch.com/
http://reviews.cnet.com/macfixit/

I then tried to boot from the OSX DVD that came with my Mac (holding down the "C" key, of course) and got hit with a kernel panic every time!

If booting from the CD that came with your Mac the operating system doesn't work, it may mean you have third party peripherals connected to your Mac that aren't compatible with that operating system. The only thing you should have hooked up to your Mac in that event are:

1. Any display.
2. An Apple wired keyboard.
3. An Apple wired mouse.
4. The original graphics card.

In event that's all you have hooked up, you have a hardware issue, and no Snow Leopard didn't cause it. Hardware can not be impacted by Software. However, it may be more sensitive to changes.
You may need to replace the RAM in your machine.

Sometimes 'C' key booting doesn't work, but using the startup manager will:

http://support.apple.com/kb/HT1310?viewlocale=en_US

That may also allow you to run the hardware test, to discover if some hardware is not working right anymore.

I have seen confirmed reports of Superdrives not working after installing 10.6. (not Mac Pro in list of those affected by update 2.1)

*The most common reason* for not booting though, that I've seen for years, is from a damaged/corrupt directory. Unplug the drive, you can then boot. Even CD/DVDs the system will still look for boot devices and can't tell or find what is present.

Given the large number of problems with external FW and optical drives, I'd say something is killing support for devices. The fact the 2009 has an SATA optical drive though should help.

I had similar things happen with my install of 10.6 and I tried the very same things you did. Finally I gave up, knowing that I had a fresh clone to fall back on. Eventually I did a clean erase and install of 10.6 and after many attempts to start up the Mac finally did. I migrated nothing. Still, all was not rosy, my Mac ran very poorly with 10.6. But right now with 10.6.1, things are going very well. Just wish I hadn't needed to go through the hassle.

One thing I can think of that might save you a trip is if you had Time Machine going for awhile. You could use that to revert back to 10.5.8 and then think about your options for installing SL again. Well, if you can't start up at all I don't know if that will work... maybe there's some way though.

I'd recommend in the future you check out this great app:
http://www.shirt-pocket.com/SuperDuper/SuperDuperDescription.html

It really saved me a lot of hassle during this changeover and makes a great companion to TM.

Good luck, Joe.

Son of a gun, I bet that was my problem too. Well done, what a web of a headache you must have had sorting it all through.
Good job, my friend, thanks for posting back. You're going to save a lot of people with a similar situation.

Nvidia....grrrr. I'm sick of that company. I still don't think the 285 is worth anywhere near the price they are asking for it.

Wow! I am glad I went with ATI! I like my new ATI 4870 - it purrs right along in my 2008 mac pro. Haven't done my upgrade to SL as of yet, but I am sure it won't be so painful.

Nvidia does have problems though.

Depuis Update 10.6.1 des problèmes son survenue avec TeamSpeex.

le Symptôme : au bout de quelque minutes de discussion une sorte d'écho qui devient incompréhensible pour les personnes, et au nivaux de l'écoute aucun problème

Version de TeamSpeex 1.0 béta (406)

Traduction Google

Since 10.6.1 Update problems occurred with its TeamSpeex. The symptom: after some minutes of discussion a sort of echo that is incomprehensible to people, and the levels of listening no problem TeamSpeex version 1.0 beta (406)

Bon jour, Mon ami

Bon chance avec: http://store.apple.com/fr?mco=NzcwNjcyMA

The 285 has a lot of potential. That's what I'm counting on... before I fly out there and start breaking things at their headquarters. That company gives Macs no respect at all. I have some faith in EVGA though. It was a great attempt to bring something special to the Mac table. I just hope they have enough clout to get Nshidia off their butts.

Video cards or not, Nadav, you know enough to have a freshly made clone all ready just in case. SL is still very buggy, and calmer heads like the Hatter are cautioning a 6 month wait until things get really straightened out.
I'm finding success with 10.6.1 but I'm still leery. 10.6.2 will go a long way towards easing my mind.

Wow, the exact thing happened to me. I installed snow leopard and within a week both of my macs died. Had them both checked out and they told me it was the logic boards going bad. What? Two of my computers die within a week and thats all they said. One of the computers was about 2 years old the other 15 months and no I didnt have Applecare.

< Edited by Host >

Pardon my butting in to this and I am sure you are going through a lot now, but how could an OS installation bring down and destroy your computers?? I can understand file corruption, or bad installs, but an OS bringing down the logic boards? I don't see how that could have happened.

Did you check your fans to make sure that they were operating at the time? Could it possibly be a bad ram chip? Again, I don't want you to take this as me insulting your intelligence, its just this is my 1st time hearing that an OS(not, snow leopard in particular, but any) could do such damage at that magnitude.

I would suggest taking the computers to a Genius and have them look. It might be an oversight. Mind me asking what kind of Mac Pros are they? 2006? 2007? 2008, 2009? Also, has anything like this ever happened to you before with any Apple equipment?

My thoughts too Nadav. I have seen several occurrences of Snow Leopard failing to completely install (without any notification) and a simple solution, reinstalling SL, solved the problem. Frankly, I see too much technical pontification on these forums when there is a simpler solution.

Yeah, I hear you. Im not all that savvy with the innards of computers. I unplugged everything, one at a time and did the whole song and dance. I then took it to a authorized shop and he couldnt figure it out either and he "just assumed" it to be the logic board. Took it to an Apple store and they said the very same thing, "didnt quite know what was going on". Just very odd two computers, different breakers, and 25ft away from each other (you know with the swine flu floating around).
So now I have parts for sale, video cards, ram, and what ever else, LOL.
Anyway what is done is done, I guess. Well I have two new computers, with applecare. If they go out guess ill go Dell, God forbid.

What a horror story. What model of Mac were those two machines. Your sig (first sig) lists a Quad, was that a G5 Quad? On both Macs no lights come on whatsoever? That would indicate the power supplies to me. It being diagnosed as the logic boards by a tech who wasn't sure what was going on wouldn't give me much confidence.
When I put the original Leopard on my G5 Dual 2.0, the machine which had been running flawlessly for 3 years died within a week. At the time I put it down to installing the new OS, but in retrospect it probably happened during my attempts to get it to run right. When you installed SL, did it work ok? Or did it run poorly and you attempted a lot of maintenance to get it to run right?

All in all a terrible outcome, I really sympathize with you.

Edit: This happened to a 09 Quad Core? You should contact Apple via phone. This is a number that used to get good results for G5 owners. Be patient and persistent and they may help you.
Apple Customer Relations 1-800-767-2775.

Message was edited by: Samsara