Neither the DW nor the heat pump are doing any better today. Worked for two hours on the heat pump with no success. It's turned into a block of ice. The usual problem when this happens is that the defrost cycle isn't being initiated by the control board. However, in this case I've verified that the board is working and the defrost cycle runs -- but when it does, the ice doesn't melt. Very odd, and beyond my skill level with these things. Time to bring in a pro.