Hi,
i have an Radeon 2600 Pro, too, same ID 9589. I use the Drivers from Netkas. You can found it on IRC Server irc.osx86.hu, Channel #radeonHD . www.netkas.org is his Page.
I have Kalyway Leopard 10.5.1 updated to 10.5.2. After the Comboupdate i have installed the Grafics Update from Apple.
Then i have searched in System/Library/Extensions fpr ATIRadeonX2000.kext, Right-Click on it, select "Open" or "Show Package" or something like that (i have German Version "Paketinhalt anzeigen"). Then open Info.PList and search the Line, which beginns with <string>... there you will find many IDs of Graphic Cards. You will notice, that there are no 9589 ID, similar like this: 0x9589001, add this in that line and safe it.
After that add the 2600 pro fix from lastexile, and it should work.
Here's actual link:
clickKS