reboot from X to 9.1 hangs

[bgbg]

I have been having a problem when booting from OS X back into OS 9.1. My startup hangs just before the little extension icons should start to march across the bottom of the screen. I think I've isolated the problem: there's something called Classic Support UI which OS X puts in the OS 9.1 system folder. If I first boot 9.1 with extensions off and then use the Extension Manager to 'turn off' the Classic Support UI, then restart again, things seem to work fine. Rebooting in to OS X and starting classic brings up a dialog box telling me that some modifications need to be made to my system folder for Classic to work, I think this means that OS X is adding another copy of Classic Support UI.

Is anyone else having a similar problem? Any idea how to fix it? I'm running with only a single partition on my HD and don't really feel like making myself a separate OS 9.1 partition.