a garage near me had a similar problem recently with a Seat Alhambra 1.9TDI 2003.It had the same symptoms as yours.A fault code was stored but nobody had the info on it.The dealer came out with their tool and still could not get the code explanation. They towed it to the dealer and received a bill for £700.00 plus the price of a immobilizer ECU. I had a feeling maybe the synchronization between the engine and immobilizer had been lost.(he didn`t have the key on the cluster flashing either).I will ask him the full story tomorrow,just for reference. HTH Andrew Ruellan