Had this happen a few times now, and can be resolved in about 5 mins with effort and patience.
IMPORTANT-Disconnect from power supply.
Remove the top cover, (two screws left and right at rear)
To the left hand of the machine, looking from the back, you will see a small black pipe connected to a circular unit affixed to the side of the machine. Disconnect the power cable via the plastic plug, and disconnect the small black pipe. After the unit is free, give a few small blows into the small plastic inlet where the pipe was connected, ( you should hear a small click), reconnect, and try the programme again. You may have to do this twice or thrice, but it does work, and resolves having an engineer coming out to do the same thing. Hope this helps.
Mike Howes, August 2011