Same problem, it appeared as if there was an obstruction but upon finding this site realised it was likely the door latch, and upon following the very straightforward instructions on the espares website link a few posts back, took out the old one, and sure enough the spring was broken. Have just ordered a new one, cost under £11 inc P&P.
Chances are if you have a different model it will still work, the exact same door latch seems to fit 51 different Hotpoint dishwashers according to the espares website, plus other makes as well.
Joe, August 2010