Why is my Photoshop CS4 crashing with Snow Leopard!?

Question

IN an attempt to make my machine work faster, an employee at the apple store said I should upgrade to snow leopard and get more RAM.
Snow Leopard upgrade--done.  version 10.6.2
RAM--ordered 2 more gigs from crucial, not installed yet.
Hardware:
Model Name: iMac
  Model Identifier: iMac8,1
  Processor Name: Intel Core 2 Duo
  Processor Speed: 3.06 GHz
  Number Of Processors: 1
  Total Number Of Cores: 2
  L2 Cache: 6 MB
  Memory: 2 GB
  Bus Speed: 1.07 GHz
  Boot ROM Version: IM81.00C1.B00
  SMC Version (system): 1.30f1
Software:
Photoshop CS4 11.0.1
Since the upgrade I have had crash after crash in photoshop and bridge.  Other times PS freezes and I have to force quit.  My tools don't work properly.  The crashes happen so often and it is hard to tell what/ if any particular sequence of events make it occur.  I can only work in PS for a few minutes before a crash occurs anywhere between 0 and 12 minutes usually.  (inconvenient because i am a wedding album designer, PS is my only way to do my job.)
A few examples of frequent problems are:
--my free transform tool gives an error saying it can't perform because of a program error.
--my key shortcuts become unresponsive when trying to use them to change between tools, especially when using the zoom tool or the brushes
--marquis tool doesn't show up when i make a selection
--images do not open when i drag or double click them from bridge to PS
--after saving and closing an image PS becomes unresponsive and requires a force quit
--my latest crash was PS just quit with no warning, everything disappeared and the crash report appeared, I had just hit command+s to save when it happened.
Things I have done to attempt to fix:
--ran all updates that are posted on adobe and apple for both products.
--font management: FontExplorerXPro cleaned all but essential system fonts from the directories and cleaned font cashes in every place I knew to look for them
--i do not have the menlo font
--uninstalled all Adobe products (unregistered, deleted preference files, used Appzapper, and then used the adobe uninstaller, then all remaining folders from adobe were thrown away and trash emptied, computer rebooted.) **this is just the most recent attempt at uninstall and reinstall, the first time i just used the adobe uninstaller which clearly did not actually remove the program and all files.  annoying.  regardless, after each reinstall, the problems continued as if nothing had been done.
--i do not use 3rd party plug-ins to my knowledge (how would I know?  could these be installed without me intentionally doing it?
I have attached my most recent crash report to this.
i need this to work.  this machine and program were far too expensive to be making my life this miserable.  Especially when the upgrade was recommended by apple. and adobe's site had no major issues to report about snow leopard.  the fact that work that should have taken 4 hours has taken me about 2 days to accomplish between crashes is a rather major issue to me.  as is the fact that i have a $3000 piece of equipment on my desk that is virtually worthless right now.
please help!

Answer 1

you have just worked a miracle in my life.  I did all of the suggestions this morning.  So far, so good, been running PS and bridge for 4 hours without a crash.  tools also seem to be working correctly.  i don't want to get too excited yet, but you might be my new favorite person in the world!
No, I didn't install rosetta with 10.6, at least not on purpose.  Best guess is that I had enabled rosetta to fix an issue i was having with PS3 last year, but I had forgotten how to turn it off and on.  I have been looking for that switch for days!  Thank you for pointing me in the right direction for that.  I had hoped that my attempts at uninstalling and reinstalling the CS would set everything back to default, but it didn't stop it from running in rosetta.  Rosetta is now off in PS and in the font manager.
I don't know about the PCC code thing, where do I find that information?  What does it mean?  I did change a few things in my PS preferences concerning the GPU settings because there was some speculation on other threads that the video card was causing crashs.  But I think I set that back to normal (enable open GL Drawings).  I don't know if the things I changed concerning that might have something to do with the PCC code stuff?
I think the com.adobe.Photoshop.plist file in the user/library/preference folder might have been the golden ticket.  when i opened that preference folder there were all kinds of things from my old PS3 in there too.  I dumped all of those and rebooted.  I have been wondering why after repeated uninstalls PS4 still had seemed to remember stuff from previous installations and also from my old PS3. (which I thought I had completely uninstalled prior to installing the creative suite 4--it was not an upgrade).  it annoyed to say the least that it retained memory of the old programs.  Now I wonder what else might need dumped out of that folder.  Should I be checking that folder for particular things periodically? 
When you say clean all caches, where do I find them?  the font manager cleans the font caches, but other than that, I don't know where to look for other caches or how to actually clean them out.
Thank you so much for answering my questions/frustration.  You have saved my sanity--and my computer from taking a two story plunge to the pavement.  you're awesome!