Some Unix advice: Use a SSH client to login to the mac when it freezes (even if your controlls behind the computer fails it will normally work)
Kill the CoH proc, you will likely have to use SIGSEGV, SIGKILL or perhaps even SIGILL.
This should abort (well it should "destroy" the proc) the updater.
If what I just wrote seems giberish ask several people you know about it or come back on it. It's slightly advance Unix stuff.