Some have reported that Kontakt 2 Player is appearing as a fully authorized standalone application, but NOT as a plugin in Logic Pro. NI has just provided a work around.
For those experiencing this problem, try doing this:
go to Mac HD>Library>Audio>Components and find the Kontakt Player 2 component.
Throw this in the trash.
Then install the Kontakt Player 2.2.3 update again to replace the component.
Hopefully this will fix the problem.