Just tested a jailbreak on my PPC Mac and I get the same result. A crash when it gets to the part where all of the text is scrolling down the screen (restore mode). And it doesn't look like something easy to fix.
It's too bad because, at that point, if you had a way to pass commands to the phone, you could easily finish the jailbreak by hand.
Anyways, the good news is that activation (once you have the PEM file on your iPhone) and deactivation do work.
So the official word is that it doesn't fully work on PPC yet.

