Jim, thanks for your response.
After reading your message, I immediately thought maybe there's something wrong with the installation on my desktop machine, so I fired up BiaB on my laptop and got exactly the same result. I tried returning to factory settings, but it didn't help.
I even tracked down the samples used in the Realtrack. The samples play back at normal speed as expected.
So, I remain completely flummoxed. Once they open, I'll ask support for advice.