Hi Bill
That certainly sounds strange. I've been running Rainwise stations since 1999 or so and have never had one to freeze up. Of course I'm here in SE Virginia and usually when we get moisture, temps begin to rise or if they fall the air drys out. Not a lot of ice storms.
You may want to contact Rainwise. I'm sure with them up in Bar Harbor Maine they should have come across the same conditions you describe.