Why does a carbonated beverage go flat after it has been frozen?

I randomly decided to search for the answer to this question so I dont know for sure, but my guess is that the crystal lattice formed by the water molecules in the beverage forces carbon dioxide molecules into the space above the liquid and then when opened the CO2 escapes. Im thinking the crystal lattice allows absolutely no extra room for molecules other than what participate in shaping it so the CO2 molecules have nowhere to go.