Using Cone of Cold (encounter power from "Rimescore") will not inflict any form of Frigid (normally 3 turns on success against magic resistance check, 1 turn on failed check) if the target is immune to the stun effect of Cone of Cold.
Hmm. I don't know if this is a bug or not, or if that's intended... Will ask. In the meantime, if you could post a screenshot of an example, that'd be great. Thank you!