Cant open multiple Vvocal windows in Platinum

not sure about solutions but keep in mind, V Vocal was discontinued in sonar a couple versions ago.
however, if you have previous versions of sonar installed (X2 and under) it will still work.
so it doesn't surprise me that you cant do that any more. support for V Vocal in later versions has been dropped.
 
you will find much better results using Melodyne. its 10 times better, more accurate then V Vocal.
theres just a learning curve.
if you are using old projects that have Vocal, well I can understand that.
but you would be better off using ARA, Melodyne.
the Vocal synch feature alone speeds up the process, that used to take a lot of time in V Vocal.
now is done automatically with a twist of a button.

Actually, I have been using both for years and Melodyne is very restricted on manipulating notes. Especially without the pencil tool. Also it it very hard to close up big vocal over shot dips and crooked vibratos in melodyne. (But only my opinion. I understand many people like Melodyne) Sometimes I think people like it because it cost a whole lot of money for the full blown version which I've owned for years. As far as artifact, they both have their particular issues. I understand when something is not supported anymore, but they should make a plugin from an older version worse.