I know this is a very old post but these machines are still on the market.
I have one about 3 years old and thanks to this forum, an occassional "tip it on it side" to drain overspill (E4 error code), a new start/run capacitor, not relying on the multi tablets for salt but adding salt to the dispenser and frequent removal of debris from the spray arm noozles (these seem to suffer badly from this and are a real pain to clear [or are we using it as a food disposal unit instead of a dishwasher - joke]) it is actually still cleaning well! Mmm, that's quite a list isn't it.
Anyway for anyone looking this is very simple to fix.
What happens is that occassionally the door doesn't quite close properly but the plastic catch on the top and inside the door panel flicks into the closed position even though the door is slightly open. (This catch is meant to hold the door firmly closed.)
NOTE: reclosing the door doesn't reset the catch but it might break it if you force the door closed. Nor will looking closly to see if the door is slightly open tell you much - the difference between the catch working properly or not is negligible; only about 3 or 4 mm in the final (closed) position of the door.
With the catch in this closed position the programme buttons are disabled by the inbuilt programming and protection circuitary.
The solution is to remove the catch mechanism from the door and, using a screwdriver lever the small plastic catch back into the correct "open" position. It is an "over centre" device held in place by a spring and whilst quite stiff it will flick back to the right position.
It's a while since I had the problem and whilst I removed mine to fix it I'm not sure if you do need to remove the catch (only two screws) or if it can be done in situ.
NOTE: Just double checked you need to remove the cover panel on the top of the door and also remove the catch mechanism to effect this repair.
NOTE2: This section of the message removed by kandlbarrett, yes the reply below is wise advice!