Is there anyway to kill a job that is already
running in the queue - but has become unresponsive?

If that job is detached you can use the Task Manager to kill the job instance of 24x7.

If it is not detached the only options you have is to forcedly terminate any child proceses created by this job, database connections, and so on whatever will release the job from hanging state.
If that doesn o help you will need to restart 24x7 scheduler.

: Is there anyway to kill a job that is already
: running in the queue - but has become unresponsive?