I have a song I recorded a couple of years ago that I like, but the lead vocal has a few flat bits. I sang it when I had a cold as it was only a demo, but now I like the version except for the little flat notes. Can Melodyne Editor using the polyphonic fix this? I only have the song in a stereo wav file. I may have a two track (left and right) in my external hard drive somewhere.

Maybe. The more stuff there is in there, the more complex it is, the harder it is to edit. But it might be possible.
 
Here's an example of the kind of thing you are talking about. Not precisely, but similar idea.

Sycraft
Maybe. The more stuff there is in there, the more complex it is, the harder it is to edit. But it might be possible.
 
Here's an example of the kind of thing you are talking about. Not precisely, but similar idea.

Did you forget a link? Hahaha!

Apparently :P We try moar links!!!

I was going to post the same link but syctaft beat me to it. The example uses audio perfect for such a process so be warned a fuller track may be more difficult. Worth a shot.

hmmm. Thanks for the link. It looks possible, but maybe more work than just re-recording the song. I may try a trial version of editor and see. I just need to fix four or five words at the tail of the note.

If I was going to attempt to try to fix a file like that, here's how I'd attempt it.
 
Assumption: The largest part of the song and vocal track is OK.... there are a few places where the vocal is off and needs fixing.
 
Use ME to capture only a short snippit at a time..... starting capture a few seconds before the bad part and ending capture as soon as it's past.  This way, ME doesn't have to calculate the entire song. Work on that part, find the vocals in it and fix them. Save it. Play it back to be sure it's right. Save it to track ...I like to "PROCESS AUDIO". Be sure to deselect the "remove plug" after the process.  Simply play forward to the next part and repeat the process as many times as is needed.
 
I work in a similar way at times on songs. But generally not in the poly mode for a full song. I have used it to easily fix a guitar note in a chord and also on piano music.
 
Let us know how it works

Update...I played around a bit last night with my editor trial and this does seem easily possible. I was able to find the notes in question and work with them. I will use guitarhacker's method tonight and see if I can get a fix I can keep. What can't get fixed can at least be deleted so I can re-sing the part in question. All in all I'm pretty impressed with Editor. I don't think I can afford to upgrade at this time, but it's on my list. Maybe it will make a nice Christmas present to my self.

I can't afford it either.......but, I'm still going to try and get it......1 more day for the sale.

Yup...ol Mel O'Dyne is one heckuva feller.  He's the devil incarnate, really.  Works black magic.  Wouldn't be without him.