I have one of those iMacs, mine is a 1.25 GHz 20" with 10.5.8 on it. Use it a lot.
I suggest getting a copy of Disk Warrior by AlSoft, it will cost about 89.00 from the Apple store or Amazon.
This what my directory looks like right now and needs rebuilding, yours is probably in worse shape than this.
This will greatly improve the overall performance of your machine and AppleWorks in particular.
Think of your hard drive as a big closet that things are put in, soon room for large things are at a premium and must be broken into smaller parts and are spread out to more than one place.
Now it gets harder for the OS to find all the parts and it has to search and that takes time and not always are all the parts found, thus missing pictures.
That is what DW does better than any other utility out there, it finds all the pieces parts and marks just where they are so that all can be found.
It does other things also but this will (with a 98% confidence level) fix your problem. Plus you will have it for when you need it again.
You will as you have lots of in and out on your drive.
Let me know.