I also tried this recipe and it did not thicken properly - I used wheaten cornflour and had also left the MC on so thought this could be the problem.  I put it all back in the next day and went and bought corn flour and added some of that and a bit of liquid and set it for another hour.  It was okay for about 20 minutes but then I also had the problem with the error message.  I have poured it into my mould and am hoping for the best however it is not looking good.