Try this link to my question at another similar site. I got the problem solved:
http://www.diynot.com/forums/viewtopic.php?p=495614#495614
It was a tricky job getting it all sorted - mainly due to my limited confidence. I needed a few tools - mole grips to get the clips off the pipes. Pliers to get the white catches to close to release the filter casing. However, you might be able to access the inside of the pump by removing the three screws you can see on the pump chamber by looking underneath when the machine is on its back. If you have the same problem then it may be possible to clean out the chamber without dismantling the filter casing entirely. If it (the pump) doesn't come cleanly off, then you may need to release the white filter casing slightly to let it clear the rim of the base.
Don't make the same mistake I did, and forget to replace the rubber washer on the inside of the pump - I had the place flooded and had to go into the pump again - but this time it was much quicker.
Hope this makes some sense. Good luck and God bless for New Year.
Gerry
December 2006