Romeo goes nuts when I open the freezer door. He'll run from wherever he is when he hears the door open and then shove his face against the plastic compartments and proceed to lick them (driving my mother mad!). He now has his own ice tray with fish shaped ice cubes that have one small treat in them.
I have just started reading the book How Dogs Think by Stanley Coren and he was discussing the hearing ability of dogs. He suggested that sometimes dogs go nuts over things we find completely normal because they can hear higher frequencies than we can. So perhaps, if 1sunnygirl's dog isn't going crazy happy at the freezer, it could be a high pitched whine coming from the fridge when it's opened? Coren also suggested that rustling leaves also make sounds at high frequencies which can be heard by dogs but can't be heard by humans.