We had the exact same problem a few weeks ago. We tried everything, It seemed as though it was stuck on the drain cycle so we kept filling it via the kettle thinking that it might eventually realise it was empty. It drained... and drained... and drained but nothing else.
My husband then decided he was going to take it apart (im sure its a man thing!). He laid it on its side and a load of dirty water started to pour out from the bottom. We had thought it was completely empty!
Anyways, when he stood it back up.... it worked again. So, Iv really no idea what was actually wrong with it but it must of been clogged somewhere and lying it down must of un-blocked it.
I know how much I depend on my dishwasher so I guess anything is worth a try.