In my case (identical symptoms on a 2.4 JTDm) it was a bad connection to one of the injectors. (I don't think Nev does oil burners, which may influence his thinking)
I was told by the engineer who fixed it that even if this is an intermittent fault the open circuit causes massive voltage spikes to be sent back along the wiring to the ECU and it all goes wrong as you describe. Your dealer/AA person can read the fault codes to tell what has gone wrong, and you should avoid running the car for too long in this state because it could cause damage.
Last edited by dastocks; 13-08-11 at 18:26.