I had the same problem with my machine. At first I replaced the interlock, which turns out wasn't at fault.
Check the metal hook shaped latch on the door to see if it has any play on it. If so, you'll need to remove the door by unscrewing the hinge on the machine. With the door off, remove the six screws holding the front rim of the door. Carefully prise off the rim. In doing so, the glass will come free. Look at the latch mechanism, you should see a metal pin holding it together. This pin had worked it's way loose over time, it only needed pushing back into place to remedy the fault. Put everything back together and the door should shut tight, and lock when the machine is put on a cycle.
If this doesn't work, I suspect it would be the interlock at fault. Only around £15 (make sure you get the correct one, I had to modify the connecting plug slightly for mine to fit) and straight forward enough to fit, though you may scratch your arms a little!
I hope this works for you
Jonathan, April 2007
