We have two G4/400 (Yikes. "PCI Graphics". Whatever) Macs, and while they run happily on 9.0, both crash in the Finder (before startup has completed) once the 9.0.4 update has been applied.
With Extensions OFF on startup, they sometimes survive a bit longer (almost a minute before the Finder freezes) during which the video does all manner of flickery, nasty things. (stock Apple/ATI cards, Studio 17 displays).
Nothing short of returning to 9.0 makes these machines happy again.
(Also see iMac mouse freeze post.)