The supervisor should be able to kill a subjob that's running on
an unreachable worker. However, in your case, it seems like the worker
machine is not completely unreachable, and that's probably causing the
system to not quite able to kill the job.
If you're able to log into the machine via ssh, you could try to reboot
the machine, or at least kill the worker process (by running
"/Library/StartupItems/worker/worker stop" as root).
Otherwise, see if the following from a command prompt on a Qube-
installed machine, as one of the qube admins, work:
qbadmin worker -reboot <HOSTNAME>
or
qbadmin worker -shutdown <HOSTNAME>
where <HOSTNAME> is your worker's hostname or IP address.