AVScan policy/job is hung

I set up an AV Policy a couple of days ago and set it as scheduled. The job failed and is no longer running but still shows up in the GUI and can't be cancellled.

The message is "Job [JOB #] not running: invalid argument The status of the policy may have changed since this page was last updated."

Any idea how to identify and kill whatever process is keeping this running? I've tried disabling the AV service but that had no effect.