If you're on Windows, take a look at UsersAppDataRoamingQueue Manager9QueueState.xml - that's where the job list is stored. I'm hesitant to tell you to just delete that file, but it would probably achieve what you are looking for.

Edit: Just move it away and see what happens. If you don't like the outcome, put it back where it was.

The actual log is located at UsersAppDataLocalTempQueue Manager9log.txt and is cleared at the end of each session.