Another newbee question:

I've just finished an arrangment of American Pie....270 bars!
Everything is fine until the end. After editing the final verse there are chords in the string and piano track that I can't clear out. The correct chords are there, but the wrong ones are there too. If I look in the track view I can clealy see there is more than one set of chords being played. I tried deleting bars and starting again, but It won't go away. How do I clean these out? Does this have anything to do with generating a song ending?
Thanks
Brian