My daughter has been trying to figure out a movie title for some time now. It's a movie about a couple that are on the verge of breaking up or something, and somehow a taxi cab driver gives some insight to the boyfriend about the woman dying or something and in the end the guy dies in the taxi cab instead of the woman. I'm not sure, but I keep thinking that christopher Lloyd was the cab driver. Please help she is driving me crazy about this movie :)

Possibly Three Days (http://www.imdb.com/title/tt0301935/)

I believe you are referring to If Only (2004) with Jennifer Love Hewitt, Paul Nicholls and Tom Wilkinson as the taxi driver. Great movie... very touching.