my original n900 broke in february, vodafone gave me a new one in april after finally collecting my old one. This n900 worked for 10days until i had the same error as you. after taking it into the shop 2times a week and ringing the customer service with vodafone GUARENTEEING it wasn't blacklisted they finally realised it was in September! and after taking 2weeks to sort it out it was then october, after using that n900 the charger port broke with in a matter of days. after 3 weeks of trying to get it repaired i was given a new device.

So far i've used just under 7months of the 13months i've paid for at £35 a month. and they won't give me a refund, the cheek of that!!!