Prevent Freeze charm doesn't work

hi,
i am playing an invoker as new char, never experienced this before with several different chars. seems my charm that is preventing freeze doesn't work at all.
I have full 75% res, but entering a map i can be instantly frozen by random mobs, not to mention of strongboxes.
I tried to switch different charm from other chars, but that also doesn't work.
build is really unplayable to the wider extent :(
can this be fixed please?