[WanderingMinstrel]

Mystery solved! I called myself a few times from my landline phone last night. One (or more) of the calls left a TSCCallerID.wav file in place and it works. Reading back through this thread, I see that someone pointed out that the TSCCallerID files are self-generating when you get calls. I just don't get calls that much. The phone part is definitely not my primary use for my TP.
So I'm good to go on the suggested reg fix.