Okay, I tried what you said. Browsing by songs on the iPod, I get the same results as trying to play via the playlist, that is -- the wrong song in one case and a "skipped" song in the other case.
But here's the thing --
re: the "wrong" song -- the ONLY thing that is the same is the name of the song ("Angel"), the artist, album, and everything else are totally different.
re: the "skipped" song -- I have no other song with the same name ("When I reach the place I'm going").
Also, I never had this problem before, as I mentioned, for the past year.
Oh, and I even tried dragging and dropping the right version of "Angel" (which would avoid the "delete unselected files" issue, I would think), but I still had the same problem *on the iPod*. As I mentioned, if I have the iPod connected and view it through MC, then I get the correct song in *both* cases.