May have accidentally discovered something - in reconnecting the Maxim TC board to the UNO, I misplaced the pins and got the same message on the serial monitor as I was getting on the LCD. This leads me to believe there is an error in the LCD sketch - but I don't know enough to know how to debug it =(
The MAX31855 has DO to UNO pin 3, CS to UNO pin 4 and CLK to UNO pin 5.