I've been wanting to try out DNA on a mixed song since I bought Melodyne Studio and have been following along with the blog post here: http://blog.cakewalk.com/subtract-or-isolate-instruments-from-an-audio-file/
 
The second step "Make sure that you have Polyphonic Mode enabled." is giving me a problem as I have found no way to force it into polyphonic algorithm. The option is greyed out and won't even select it on default. Anyone else have this issue?

http://www.celemony.com/en/melodyne/functions
 
Looks like polyphony may only be a feature in the editor version.

Also the studio version is only 32 bit.
 
 

You need Melodyne Editor for polyphonic mode

I have Melodyne Editor.  It's pretty awesome for a lot of polyphonic sources- as long as there are pretty strong transients (like an acoustic guitar, percussion, many types of pianos).  But on distorted guitars you'd wanna make sure you also track it clean- apply Melodyne- then re-amp.  On mixes, I'd have to say it aint prime time at all.  Some may disagree but I've gotten mostly flange-sounding stuff when I appy it to deep material like full mixes. 

I thought I mentioned it, I guess not. I own Editor.

That doesn't sound right. Do the other editor functions (e.g. Pitch drift or the advanced timing tools) work for you?

Verify the Editor license is running. To check it, open the Melodyne menu Help > License
The license dialog will show which version is running.