Is it possible my cream was too cold prior to whipping?
Sometimes whipping cream separates a little bit in the package and forms a solid layer on top of the liquid cream. This is normal and should not effect its whipping properties. 

The few times I have had a hard time whipping cream has been on really hot days or when the cream doesnt contain enough fat. The cream has then separated in the same way as you described. Your cream should have about 40% fat. 

You should easily be able to tell if the cream has gone off by smelling or tasting it.