Cannot install any updates 10.5.8 ibook G4

Hello,
Using software update or manually downloading updates works fine but once I try to install them I get a , "Install Failed" alert. "The installer could not install some files in "/".
Updates tried, security update 2009-006 and Safari 4.04
I have run the disk utility that came on the Leopard DVD (10.5.1) using "repair disk" and it came up with no problems. After I ran this repair disk utility I tried installing updates again with same result.
I have read DiskWarrior might fix it but that is $100.00!
I installed a new hard drive 6 months ago (300GB WD) along with Leopard and it has worked flawlessly. Actually everything works now, it is just that I can't install any updates. I thought of backing up and doing a clean install of Leopard again but I would rather not if possible. Thanks for any thoughts or ideas.
Patrick
ibook G4 1.42 GHz memory 1.5, 300GB (284GB available)

Try running Repair Permissions from Disk Utility.

That's a no go, then try downloading and installing the 10.5.8 combo update.

Bobtomay,
Thanks for the response. I ran "Repair Disk Permissions" and within seconds a box appears: " First Aid failed" Disk utility stopped repairing permissions iBook G4 because the following error was encountered:
The underlying task reported failure on exit

Sounds to me like the drive may be failing.

Download Smart Utility. Once open click on the 'More Info' button in the 'Tests' section. I'd probably go ahead and run the long test since you're having issues.

You get 4 free uses or 30 days free trial.

Regardless, get your drive backed up if it's not.

I just ran the "Smart Utility".
I selected the long test like you suggested.
It "Completed without error.
Power On Hours: 175
Temperature (C) 44
Last Test Time: 174

it sounds like data corruption to me, in which case a clean install would fix the problem if it's not a hard drive issue.