I have verified a few things, during the install:
1. The 10.6.8 upgrade will force a reboot (where you can't touch the mouse) if your active window it NOT on multibeast, so make sure you have multibeast not only open, but as the active window. (this is not mentioned in the guide)
2. When running multibeast after the 10.6.8 upgrade, repairing permissions always failed for me. All the rest was ok, so user DSDT, plus rebuilding cache.
When you go into Disc Utility and try to verify or repair disk permissions you will get an error:
"Repair/Verify permissions failed: Framework unable to communicate with DiskManagementTool"
Not sure if that helps or not. Now I'm going to retry to reboot and keep my fingers crossed.
EDIT:
Failed again, same error as before, boot bar below the apple goes about 1/4 of the way, then disappears and I get a white screen, but this time the mouse moves.