Leopard 10.5.5 Update - Freeze on Boot, Apps Freeze, Screen Glitches, etc..

Question

After upgrading to Leopard 10.5.5 I've been experiencing MANY issues which I think are related to how 10.5.5 works with my video card (see below for system details):
If I shut my computer down it takes about 20 tries before it will boot completely without video glitches and freezing
Each time I start the computer it gets a little farther in the boot process before freezing
I have tried starting in Safe Mode but the computer never gets past the Apple logo and spinning wheel
I have tried Zapping the PRAM and this seems to help get a little farther in the startup process but doesn't do much else
All applications will freeze up randomly, giving me either a glitchy screen, spinning color wheel or both
If I ALTCMDESC during a application freeze, the Force Quit screen appears and the frozen program will work okay again (without me having to quit it)
Sometimes the computer will freeze and the screens will completely and flash different colors. This requires me to hold down the power button until shutdown
Repairing disk permissions gives the same error after every time I startup. As if every time I shut the computer down some disk permissions get messed up.
I have uploaded images of the screen glitches I have been getting as well as a text document with my Disk Permission Repair Report here
http://www.yousendit.com/transfer.php?action=batchdownload&batchid=Y2o4Y050dENYSHhjR0E9PQ
If anyone has experienced problems similar to these and has any suggestions on how to fix it without rolling back to 10.5.4 please share.
Thanks
Hardware:
+Model Name: Mac Pro+
+Model Identifier: MacPro1,1+
+Processor Name: Dual-Core Intel Xeon+
+Processor Speed: 2.66 GHz+
+Number Of Processors: 2+
+Total Number Of Cores: 4+
+L2 Cache (per processor): 4 MB+
+Memory: 4 GB+
+Bus Speed: 1.33 GHz+
+Boot ROM Version: MP11.005D.B00+
+SMC Version: 1.7f10+
Software:
+System Software Overview:+
+System Version: Mac OS X 10.5.5 (9F33)+
+Kernel Version: Darwin 9.5.0+
+Boot Volume: Root+
+Boot Mode: Normal+
Diagnostics:
+Power On Self-Test:+
+Last Run: 11/10/08 10:33 AM+
+Result: Passed+
Graphics/Displays:
+NVIDIA GeForce 7300 GT:+
+Chipset Model: NVIDIA GeForce 7300 GT+
+Type: Display+
+Bus: PCIe+
+Slot: Slot-1+
+PCIe Lane Width: x16+
+VRAM (Total): 256 MB+
+Vendor: NVIDIA (0x10de)+
+Device ID: 0x0393+
+Revision ID: 0x00a1+
+ROM Revision: 3011+
Displays:
Message was edited by: DarkForestFilms

Answer 1

Screen glitches and system crashes that still persist even while booted from the Install Disk points very strongly toward a hardware problem, even if AHT can't find it. Things to consider:
AHT asks that you disconnect non-essential pheriphals to run the test, & it doesn't test them. But you can just by removing them temporarily. (Note the the installer disk will boot the system even if no hard drive is installed.) Extend this to everything that can be removed without making the Mac Pro non-functional, including anything non-essential in its PCI slots.
Even though third party RAM is more suspect than Apple-supplied RAM, the latter can go bad as well. Try every combination of the minimum number of modules needed to run the OS on your Mac Pro to see what happens. You can also try extended RAM testing with Rember. You may also find the "Press" links at the Rember web site useful for more info about this, for example Troubleshooting Tools: Memtest and Remberfrom MacFixIt.
Physical inspection of the hardware sometimes also helps: are all cables & connectors (both internal & external) tight & in good condition? All covers in place & properly oriented? Any foreign objects lodged anywhere in the case, especially small bits of metal or other conductive substances? Mac Pro's are very cleanly designed inside as well as out, but it is still possible that the problem is caused by something like this.