If you uninstall an older (X2 or before) version of Sonar, it will delete VVocal from your system, even if you still have a newer-older version.
E.g. I uninstalled 8.3 and X1 while keeping X2 & X3. Then I installed Platinum. VVocal was gone from the system, but somehow VVocal was still in the RFX menu. Platinum crashed from trying to add RFX VVocal. Also when I opened an earlier project in Platinum that has VVocal on it, Plat crashed. To be fair, X3 and probably X2 also started behaving this way.
I reinstalled X2 over itself to get back a working VVocal. Then I reinstalled Platinum to get the latest versions of various dll's that X2 seemed to put in the shared & common areas.