I've poked around more. For one thing, the file BasicSimulation.scala is not getting updated.
Yes, I hit "Stop & Save" at the end of the recording session.
Yes, when I start, I get a warning that I am about to overwrite an existing simulation. I choose "Yes" at this point.
There is no error message when I "Stop & Save", so I expect that the file gets saved as specified. However, it still holds the original code.
So ... not only does my file not save, but the supplied recording session fails to function.
I've also tried changing the listening port to 80 (the port shown in the failing playback output), but that doesn't help, either.
Any ideas?