Over 400 GB lost: disk utility is no help

[NeeLonMac]

I thought it's nice weekend to clean up my iMac G5.
So yesterday I backed up all my data on an external hard disk. Today I wanted to clean up my computer and make extra partitions.
All went well, I had a partition of a few GB's for my mounted installation disk of OS X Leopard.
My second partition of a few GB's to install Leopard to.
The rest (over 400 GB) turned in the third partition for my data.
Then I saw there was 1.3 GB left, unused.
That's not what I wanted, so I tried to put those in the third partition of over 400 GB. Something went wrong and now I have 1.3 GB free space besides my first two partitions, and it can't find 400 GB of my HD.

What can I do to fix this?

Also the HD is only 2 years old.

 

[simsaladimbamba]

Can you repartition the HDD? Can you make a screenshot of Disk Utility and its Partition Tab and attach it to your next post?

 

[NeeLonMac]

Not at the moment, I figured updating everything to 10.5.8 might be a good idea. So it's busy for a while (now on phone).
The 1,3 GB can't be formatted, or it must takes hours to be formatted.

 

[NeeLonMac]

Fixed!
After the reboot of the updates, the 1,3 GB of free space suddenly was 413 GB.

I did earlier a sudo rm on a cache. I got that line from another forum about a similar problem. They said the free space was made into an invisible document somewhere and clearing that cache would fix the problem after reboot.
But I didn't find it back after reboot.

After updating from 10.5 to 10.5.8 and another reboot it was there again, so I did something good I guess. Maybe a newer version of Disk Utility?

Much thanks for the willing of helping anyway!