I'm using Kontakt 5.5 within Vienna Ensemble Pro 5.4.13715 in a 4 core i7 Windows 7-64 machine with 12GB RAM.
I just upgraded from Kontakt Player 5 to Kontakt 5.3, then updated 5.3 to 5.5 (just now), and when I create a new plugin/Kontakt it opens as 5.3, and some of my new libraries won't open. But when I open Kontakt in stand-alone mode it opens fine as 5.5, and all my libraries load.
Is there somehow a 5.3 plugin left in a folder somewhere? Any idea how I can fix this?