I'm actually doing the same thing right now myself. The bad news is that ASU doesn't find anything to patch in either update (combo or regular... and I've done both) and when I try to install it always hangs at the finish line with the "install scripts" so the only way I've found that I can update my system is to boot into another installed system (I use a simple 10.5.4 LawlessPPC install without upgrades form an external HD) and then select the proper install destination from within the installer. I'm still messing around with getting it to work just right, but so far I'm having very very slow progress.

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