Oy, the movie-musical vs. musical-movie thing again...
Hairspray is a good example. The original was a musical-movie; the 2007 version was a movie-musical.
Maybe it's just me, but just because characters dance (or sometimes sing), doesn't make it a musical, especially when it's something their character does as part of the story.
Yes, Cabaret (arguably) falls into this category, but then so does a mixed bag like Footloose, Dirty Dancing, Saturday Night Fever, Walk the Line, Living Out Loud...
Just because there's a plane crash in the English Patient, I wouldn't call it an action movie. And Titanic has a sex scene, but it's ain't a porno. (Yes, this last paragraph is extremely sarcastic.)