Have you blown the dust out layely?
Does it do better if allowed to cool?
One way to test is to Safe Boot from the HD, (holding Shift key down at bootup), run Disk Utility in Applications>Utilities, then highlight your drive, click on Repair Permissions, Test for problem in Safe Mode...
PS. Safe boot may stay on the gray radian for a long time, let it go, it's trying to repair the Hard Drive
Reboot, test again.
If it only does it in Regular Boot, then it could be some hardware problem like Video card, (Quartz is turned off in Safe Mode), or Airport, or 3rd party add-on, Check System Preferences>Accounts>Login Items window to see if it or something relevant is listed.
Check the System Preferences>Other Row, for 3rd party Pref Panes.
Also look in these if they exist, some are invisible...
Do you have the AHT disc?
If not, download and burn AHT v1.2.6 to CD and test your machine:
Test memory with Rember or Memtest X.
No PCI cards or such installed, right?
If so, remove for troubleshooting purposes.
Have a second hard drive or spare volume? Clean install OS X and see how it runs.
KPs and freezes aren't always hardware.....
Doesn't sound prommising, but anything from a failed hard drive to a failed CPU could be the issue.
Will the machine start up in Open Firmware? If it will, you can check the status of some of your hardware.
Please read, learn and apply the following:
Of particular interest are in examples 2 and 3 for checking the RAM report and the CPU report.
Thanks, Japamac. I will look into this as soon as I can. I was able to reinstall the OS on another of the 4 hard drives and still getting freezes here and there, particularly after a sleep and when there are more than 4 hard drives in the machine. It was a real push though to where it is now.... freezes galore prior to this new OS instillation.
I was able to reinstall the OS
Good. Progress is good...
Since it's booting, Open Firmware boot is likely unnecessary (for now).
Check the System Profiler/Hardware for proper reports of memory and CPU.
Check the Diagnostics report.
Open Console and look for logs relating to failed processes after sleep wake event.
Pull all but the current boot drive. Lets limit possible suspects.
Pull all PCI cards (if any).
Since it's running, download Memtest X or Rember and test your RAM.
Testing all RAM in Single User mode (use Memtest) is best.
I'd test regardless of the system report.
If the RAM test is clean, then we have eliminated another big possibility.