The flexi-pipe and especially the outlet pipe, which it goes into, is most like blocked with "gunge". Take out the machines flexi-pipe from the waste pipe and use a coathanger wire to try to unblock the waste pipe and clear the gunge which collects from the sides, which eventually leads to blocking it..
Pour some water down it and see if it dissapears, if it does, Job Done!
Return the flexi-pipe to the waste pipe and pour water into the machine. Switch on to drain and see if this cures the problem and will also help further clear the flexi and waste pipe.
Good luck.
Davymac
July 2009