Had this problem several times on the exact same model. the reset button is inside the workings of the dishwasher. I found the first time it tripped for us I needed to partially dismantle the dishwasher to find out what was broken. Once I had figured out what needed doing, subsequent resets only involves removing a couple of access panels and sticking your arm in.
A) To find the reset button for the first time.
1) Unplug the diswasher. The top of the unit is a one piece panel fixed by two screws under the rear lip. remove screws, lift the back up and slide forward to remove. Lay the unit down on it's left hand side. Use towels to mop up any water that leaks out.
2)the plastic plinth trim on the base has 2 screws holding it on. remove these, then put your thumb down behind the front feet and push down hard to release the clips holding the plinth on.
3) There is a flat white plastic trim at the bottom front [at the side] of the unit, held on with one screw. remove it.
4)If you look behind where the front plinth sat, you will see two black plastic snap in access panels. the topmost one (would be the one on the right hand side if it was stood upright) is the one you would use in subsequent times when sticking your arm in to reset the cut-out.
5)Working your way round the metal side panel, remove all the securing screws and lift off the panel.
6)You can now see the internal workings of the dishwasher. Towards the back of the unit, and about an inch in from the side of the dishwasher (that you have just removed) are two wires going to the reset switch itself.
7) Between the two spade connectors attached to this switch is the reset button. press it in and you should hear an audible click. The overheat switch is now reset!
8) re-assemble in reverse order of the above.
B) Now you know where the switch is, next time it happens, you only need to remove the white plastic plinth (having laid the dishwasher down on it's left hand side), remove the black plastic access panel I mentioned earlier, and stick your arm in [You DID unplug it from the power supply, didn't you?], feel around for the reset switch and press the button. much easier and only takes about 10 minute.
Hope that helps
Colin Langdon, January 2006