My work MacBook Pro is freezing too. Random freezes where you can't do anything but a hard reset. I have completely reinstalled the OS, cleared the PRAM, repaired the disk with Disk Utility and checked the hardware with the Apple Diagnostic tool and Tech Tool Pro.
I have exactly the same problem. I have gone a bit further by using Disk Warrior and ensuring everything is completely up to date. I have noticed as of late that the freeze is occurring more when the monitor goes dark into monitor sleep mode and then when I try to use the computer again I get the spinning ball of death and can't actually make any changes to my programs. The cursor still works though; the machine would freeze with only the mouse still responding. But nothing else would work. I couldn't switch apps, couldn't quit anything, the Finder wouldn't respond, and the machine wouldn't recognize mouse-clicks or keyboard input. It would just let me move the mouse back and forth... and nothing else. I have combed the net and repair manuals looking for a fix.
I speculate that it might be a problem with firmware or SMC or some other default settings that wouldn't be corrected by re-installing OS as that did not fix the problem. I am getting desperate

Any ideas would be greatly appreciated. I have a MacBook Pro 17 purchased exactly one year ago. This is my first Mac since the 90s and as such I am a bit of a newbie on Terminal and any internal coding so if you could keep that in mind
Some additional information:
- when I have to do a hard shut down, I have a very hard time re-starting the computer i.e., I have to reset pram, go into single user mode, use install disk, and so on until at some point the computer recognizes the hard drive and finally re-starts
- I have not been able to use Open Firmware since this problem has started
- I have prepared a firmware update disk to re-install firmware (I do have the latest version already installed), however have not been able to emulate the correct conditions as described by Apple in order to carry out the re-install
- The computer heats up quickly when in this stasis mode as it looks like cooling system is not being controlled properly and/or working
- When I do get the computer to work everything works great until the next freeze up (can be several days later) happens again
- This started happening Sunday Sept 17th