Do you have a dual processor machine?
It appears there is problems with OSX when running on dual processor machine, hence, no dual processor machines currently being built. I have been trying to get an answer from apple since OSX was released, but, I never get any reply.
One solution is to switch of one processor. This is supposed to work but I have refused to try it. I have tried the latest version of OSX (10.0.4) and the latest draytek driver.
I am assuming that it will be fixed in 10.1.
Nigel