I think it can be some kind or hardware equipment protection behavior rather than a problem. Just hold down the power button. Assume it's not a force shutdown, when your machine has already logged out of the OS. It is waiting in DOS or something like that - nothing else...
well the os doesnt log something correctly and doesnt shut down, when i hold the power button down and shut it down after its just black screaned (still running) and then in the morning i turn it on and go into xp, check the mac drive with macdrive and i cant access it and it posts an error that the drive is faulty.
which clearly means the os isn't shutting down and logging everything right..
i then have to reboot into osx then restart from withen osx and boot into xp in order to have all the files i need available.