update so far:
asked vodafone if they had blacklisted it, they said they hadn't. i sent it back to nokia who said tmobile had blacklisted it. i have never ever used tmobile on any phone. so i phoned tmobile to find out why, and they said the imei number is a n900 that was sold by tmobile and has been reported stolen and that i have been sold a stolen phone. i have had this phone since october 2009 and i bought it from new. they wouldn't even let me email a copy of my purchase order to prove its mine. so at the moment mobile phones direct are looking in to it. unbeliveable