Ah, thanks man. That did it. I either never noticed that behavior before, or else maybe I did have that box unchecked until... tonight. Weird - I don't think I could've possibly ticked it inadvertantly... Anyway, it was just disturbing to see the program blow right past a blue A marker like it wasn't even there...

Btw, for whomever else it might help, the "Vary Style in Middle Choruses" checkbox is under Edit>Settings for This Song.