if you switched the water supply off whilst you were away this would account for machine filling up with water due to low water pressure.this causes the inlet valves to release and let water in
If the water was left on and it filled replace the inlet valves
e90 is a communication error between the main pcb and the user interface.usually it is a bad connection on the edge connector on the user interface in the control panel.there will be a blue wiring loom going to the front.that is the one that gets loose connections.remove/clean and refit connector to user interface usually sorts intermittent E90 errors
ck, August 2011