It's possible that Melodyne detected that note an octave lower than it actually is.  Below is an excerpt from the following URL: http://helpcenter.celemony.com/editor2/en/singletrack_tour_02_ede.html
 
Depending upon the material, it can be necessary to edit the detection manually and reassign detected notes. This applies in particular to polyphonic material, in which overtones are sometimes interpreted as independent notes, and not all the notes actually played are invariably displayed. With melodic material, a note may occasionally be confused with the same note an octave higher or lower. Before editing such material, you need to reassign these notes to their correct pitches; otherwise tonal artifacts could be produced when the material comes to be edited. The aim is to ensure that the notes you see in Melodyne correspond as closely as possible to the notes actually played.
 
HTH

I always copy the vocal track that I intend to edit with melodyne to another track, because undo doesn't always undo. Just a thought. And I haven't changed my buffers since I was having a crash problem, melodyne's performance hasn't suffered, I usually get excellent results. BTW, you got really good ears to hear 9cents. Congrats!

Try to activate "Show intended notes" from the "view" menu of the Melodyne window. Then move the blob an octave higher/lower to match the correct octave. Otherwise the formants will be interpreted wrong and it will sound like you described. Moving the blobs without the activation will make it even worse...
 
Edit: Forgot to point out that you have to use the "Detection Mode" (the arrow with +-)