Logic Pro 8 Melodyne and tempo

Just installed Melodyne to salvage my limited ability to sing.

Transfered part of a vocal. Upon playback through Melodyne all is well until bars 80-83. The tempo track in these bars goes from 67 bpm to 49 bpm. By bar 81 the vocal is clearly behind the music when played through the plugin, although the original file is on-tempo (though most certainly not in-tune!). What must I do?