I've been having the same problem, Vicki...
I'm starting to think I might take Karen's idea of using one of those heated birdbaths for the bottom of a nester to see if that could keep the eggs from freezing!! SO frustrating to get a gorgeous egg and then see it is frozen and cracked...
you'll have to let me know how it goes if you try them. I'm not sure what I'm gonna do yet...the only ones I've had a problem with is my two outbuildings...and those are going to be changing here soon, so I'm not too worried. The birds I'll be using for breeding will be moved into the barn where its much warmer luckily.
shot off a couple emails too you by the way.