Hi, by no means am i an expert on fixing washing machines, however, I have the exact same model and i think i had the same problem before. Does the tub seem really easy to move around compared to before? Does the machine stop mid spin due to it being out of balance?
I found that there is a small spring on the top left hand side that attaches the tub to the washing machine frame whose job is to keep the tub balanced. If the spring has come off then the tub will wobble around and trigger the machine to prematurely stop mid cycle.
Its easy to get to: open the lid and you will see the 2 screws that hold the plastic rim down under little tabs. Take these out then you can remove the whole top, make sure you unscrew the little earthing wire on the back. If the spring is at the top and visibly attached like I mentioned then bummer its not the prob sorry for getting your hopes up. But if the spring has come undone like mine did, it is not visible and has prob slid down to the bottom. All you do is reattach the spring and you should be fine. Good luck.
Alex Stephens
February 2008