Yep, Barmaid's right, give it a whip first. I made the mstake of freezing an unwhipped carton and it was awful, a whipped one turned out fine, needed another whipping though if I remember rightly.
If you put it into a lidded container, and shake it around for a while, then it will turn into butter, pour off the whey, rinse the butter, and make some toast!!!