Actually, I wasn't *trying* to clone anything.
While testing the job after having set it to use the basic Execute task to run the script, the Client wasnn't showing how the Job test was running and the actions I expected the script to cause weren't happening.
After closing the Edit Job form while the test was still running, I tried refreshing the status to no avail with F5, and then tried refreshing the status by collapsing and re-expanding the Job info, and then finally by disconnecting and re-connecting the client.
It was upon re-connecting that the first Unhandled Exception appeared.
(Why didn't I think to include this detail in my original post? I dunno; I know better than that.)