Security Updates 2006-007 & 2007-003 | Need Advice

Question

I have never had any problems with the security updates before, but last Fall, when i downloaded Security Update 2006-007, my entire computer froze. I wrote about this at the time but my problem was never resolved. (My computer model and info are listed below.)
No matter what i tried, i always ended up having to shut my computer down by pressing down on the button. I tried restarting several times and it was always completely frozen. The cursor would move but would not open anything.
Finally, i ended up having to reinstall my OS from the disks all over again. I tried installing the 2006-007 update again, and the same thing happened. Had to completely reinstall my OS.
I didn't like the idea of not having the security update, but since my computer was not functional after installing the update, i opted not to get that update again.
Well, i downloaded the 2007-003 update, and although i saw that the 2006-007 was combined with that update, i figured that maybe the bugs had been worked out or something. Stupid me. The exact same thing happened with this new combined update.
I need some computer genius to figure out why in the world this is happening. I just don't get it.
Like i said, i feel insecure not having the updates but my computer just won't function when i install these particular ones.
I have tried so many times and keep having to reinstall my OS.
What could be causing this?
I know this is happening to other people, too, as i've read the other threads about it and also posted in at least one of them.
Oh, and in case anyone is wondering - although my PowerBook is getting along in years (nearly five years old), it still works great! I mean, it's just a fine computer that has never given me any serious problems. Without those particular security updates, it still works wonderfully. I'm religious about repairing permissions and general maintenance.
But these security updates render it useless. So i'm afraid to install them, they seem to be bad for my computer and i'm really tired of having to reinstall my OS.
I hope someone can help. Thanks.
PowerBook G4   Mac OS X (10.3.9)   Ti 800MHz 1GB RAM 100GB Internal Drive
PowerBook G4   Mac OS X (10.3.9)   Ti 800MHz 1GB RAM 100GB Internal Drive
PowerBook G4    

Answer 1

Thanks for your reply, scapesuiter.
I suppose i can rule out third party software, as, after i reinstalled my OS after the first freezing (after 2007-003), i did not add anything else. At that point there was nothing on my computer but what came on the original install disks. I tried downloading and installing 2007-003 again and the same thing happened, and i had to reinstall again.
However, i do have 1GB RAM that i did not order from Apple. My computer originally came with 512 but i bought more some time ago (can't remember exactly when).
I also bought a new hard drive, also not from Apple, at around the same time.
But i should say again that i've had no problems since getting the new hardware, other than with these particular security updates (2007-003 and 2006-007). All the other security updates went well, as well as all other software updates.
(I also did a hardware check with my Apple Hardware Test disk and it indicated that everything was working fine.)
PowerBook G4   Mac OS X (10.3.9)   Ti 800MHz 1GBRAM 100GB Internal Drive