Hi,
I get this quite often, its usually caused by sweet papers left in my son's trouser pockets!
Easy solution, your pump filter is blocked. There is usually a tube behind a panel at the bottom of the machine, undo this and drain into a suitable container, then unscrew the drain plug and clear the blockage (usually fluff or sweetpapers!). This is probably in your handbook under emergency emptying/drain pump clearing. Beware lots of water can come out!!
Tony Coates, May 2006